We present software on total energy calculation by quantum mechanics first principle method with a graphic user interface (GUI). Total energy calculation in this software is based on numerical analysis of time-dependent density functional (the used numerical method is finite difference time domain). QUMEC package has been equipped by common exchange-correlation energy terms with electron spin polarization calculation. With this package, users can calculate the total energy of the free particle, bulk materials, and materials with free surfaces at the atomic scale. The package is tested by several physical subjects, i.e., the surface energy of nano-LiCoO₂ and diffusion constant of lithium atoms in LiNi­_0.5Mn_1.5O₄.

Two-dimensional (2D) materials have been a research hot topic in the passed decades due to their unique and fascinating properties. Among them, mechanical properties plays an important role for their application. However, there lacks an effective tool for high-throughput calculating, analysing and visualizing the mechanical properties of 2D materials. In this work, we present, mech2d package, a highly automated toolkit for calculating and analysing second-order elastic constants (SOECs) tensor and relevant properties of 2D materials with considering their symmetry. In the mech2d, the SOECs can be fitted by both strain-energy and stress-strain approach, where the energy or strain can be calculated by first-principles engine, such as VASP. As a key feature, the mech2d package can automatically submit and collect the tasks from local or remote machine with robust fault-tolerant ability, make it suitable for high-throughput calculation. The present code has been validated by several common 2D materials, including graphene, black phosphorene, GeSe2 and so on.

Plasmodium falciparum dihydroorotate dehydrogenase (PfDODH) is one of the enzymes currently explored in the treatment of malaria. Although there is currently no clinically approved drug targeting PfDODH, many of the compounds in clinical trials have [1, 2, 4,] triazolo [1, 5-a] pyrimidin-7-amine backbone structure. This study sought to design new compounds from the fragments of known experimental inhibitors of PfDODH. Nine experimental compounds retrieved from Drug Bank online were downloaded and broken into fragments using Schrodinger power shell; the fragments were recombined to generate new ligand structures using BREED algorithm. The new compounds were docked with PfDODH crystal structure, after which the compounds were filtered with extensive drug-likeness and toxicity parameters. A 2D-QSAR model was built using the multiple linear regression method and externally validated. The compounds electronic behaviours were studied using DFT calculations. Structural investigation of the six designed compounds, which had lower binding energies than the standard inhibitors, showed that five of them had [1, 2, 4,] triazolo [1, 5-a] pyrimidin-7-amine moieties and interacted with essential residues at the PfDODH binding site. In addition to their drug-like and pharmacokinetic properties, they also showed minimal toxicities. The externally validated 2D-QSAR model with R² and Q² values of 0.6852 and 0.6691, confirmed the inhibitory prowess of these compounds against PfDODH. The DFT calculations showed regions of the molecules prone to electrophilic and nucleophilic attack. The current study thus provides insight into the development of a new set of potent PfDODH inhibitors.

The structures of Ag complexes with dimethyl amino phenyl substituted phtalocyanine m[dmaphPcAg]q of various charges q and in two lowest spin states m were optimized using the B3LYP method within the D4h symmetry group and its subgroups. The most stable reaction intermediate in the supposed photoinitiation reaction is 3[dmaphPcAg]-. Group-theoretical analysis of the optimized structures and of their electron states reveals two symmetry-descent mechanisms. Stable structures of maximal symmetry of complexes 1[dmaphPcAg]+, 3[dmaphPcAg]+, 2[dmaphPcAg]0 and 4[dmaphPcAg]2- correspond to the D4 group as a consequence of the pseudo-Jahn-Teller effect within unstable D4h structure. Complexes 4[dmaphPcAg]0, 1[dmaphPcAg]-, 3[dmaphPcAg]- and 2[dmaphPcAg]2- with double degenerate electron ground states in D4h symmetry structures undergo a symmetry descent to stable structures corresponding to maximal D2 symmetry not because of a simple Jahn-Teller effect but due to hidden pseudo-Jahn-Teller effect (strong vibronic interaction between excited electron states). The reduction of the neutral photoinitiator causes symmetry descent to its anionic intermediate because of vibronic interactions that must significantly affect the polymerization reactions.

The emergence of the semiconductor industry in the early 1960s resulted in a significant stage in the evolution of computing when large computational problems, as typified by the application of the discrete Fourier transform (DFT) to the task of spectrum estimation, could suddenly, with the availability of suitable algorithms, be solved in close to real time fashion. This paper provides a brief and meandering account of the history of the DFT’s various solutions, referred to generically as the fast Fourier transform (FFT), the algorithm being chosen for its mathematical elegance, practical significance and ever‑increasing range of applications. We touch upon a few of the most striking personalities, places and events that were encountered along the way and look, in particular, at the recent British contribution to the journey.

The photophysical properties of Cu(II) complexes with 5,10,15,20-meso-tetrakis(phenyl)porphyrin and 5,10,15,20-meso-tetrakis(N-methylpyridium-4-yl)porphyrin were examined by luminescence and femtosecond time-resolved absorbance methods respectively. These studies were supported by DFT and TD-DFT calculations which highlight the important role played by a ligand-to-metal charge-transfer states in directing the system towards either intersystem crossing to the triplet hypersurface or coordinative expansion to a five-coordinate quasi-stable intermediate. The latter processes occurs when the porphyrin is photolyzed in the presence of suitably located Lewis bases. Femtosecond time resolved absorbance measurements on Cu(II)-5,10,15,20-meso-tetrakis(N-methylpyridium-4-yl)porphyrin confirm that the coordinative expansion in water occurs in approximately 700 fs while crossing to the triplet hypersurface takes approximately 140 fs in the same solvent. These processes are mutually exclusive, but both can occur simultaneously depending on the environment of the porphyrin. The ratio of the two processes depends on the relative orientation of the Lewis base with respect to the copper atom at the time of excitation. As a consequence, copper porphyrins such as these, are excellent probes to the environment of the porphyrin, and can be used to identify the location of the porphyrin when interacting with DNA fragments.

Molecules sourced from marine environments hold immense promise for the development of novel therapeutic drugs, owing to their distinctive chemical compositions and valuable medicinal attributes. Notably, Talarolide A and Talaropeptides A-D have gained recent attention as potential candidates for pharmaceutical applications. This study aims to explore the chemical reactivity of Talarolide A and Talaropeptides A-D through the application of molecular modeling and computational chemistry techniques, specifically employing Conceptual Density Functional Theory (CDFT). By investigating their chemical behaviors, the study seeks to contribute to the understanding of the potential pharmacological uses of these marine-derived compounds. The investigation involves the utilization of molecular modeling and computational chemistry tools, with a specific focus on Conceptual DFT. These techniques are applied to examine the chemical reactivity of Talarolide A and Talaropeptides A-D, shedding light on their potential for interacting with various biological targets. The research reveals insights into the chemical reactivity of Talarolide A and Talaropeptides A-D, uncovering active reaction sites and potential biological targets. Talarolide A demonstrates robust anti-inflammatory properties and antitumor activity against diverse cancer cell lines, while Talaropeptide A displays antimicrobial efficacy against both bacteria and fungi. The study underscores the significance of comprehending the chemical reactivity of natural marine products for advancing pharmaceutical development. By employing computational tools such as Conceptual DFT, this research uncovers crucial information about the active sites and potential targets of Talarolide A and Talaropeptides A-D. The findings contribute to the broader understanding of marine-derived peptides and their prospects as pharmaceutical agents, though further investigations are necessary to fully elucidate their pharmacological attributes.

Monolayered MoS₂ is energetically most stable when it has a 1H phase, but 1H to 1T phase transition (1H→1T) is easily realized by various ways. Even though magnetic moment is not observed during 1H1T, 0.049 µB/MoS₂ is obtained in local 1T phase; 75% 2H and 25% 1T phases are mixed in (2×2) supercell. Furthermore, non-negligible magnetocrystalline anisotropy (MCA) energy is occured. Most magnetic moment as well as MCA are originated by 1T phased Mo atom5 in the supercell, while electronic structures of other atoms are similar to non-magnetic. Due to this, magnetic/non-magnetic boundary is created in the monolayered MoS2. Our result suggests that MoS₂ can be applied for spintronics such as a spin transistor.

Computational investigations on the BPE-ligated Cu-catalysed enantioselective addition of enynes to ketones were performed with DFT method. Two BPE-CuMes catalysts, BPE-CuMes and (S,S)-Ph-BPE–CuMes, were employed to probe the reaction mechanism with the emphasis on stereoselectivity. The calculations on the BPE-CuMes system indicate that the actvie metallized enyne intermediate acts as the catalyst for the catalytic cycle. The catalytic cycle involves two steps: 1) the ketone addition to the alkene moiety of the metallized enyne; 2) the metallization of enyne followed by the release of product with the recovery of the active metallized enyne intermediate. The first step accounts for the distribution of the products, and therefore is the stereo-controlling step in chiral systems. In the chiral (S,S)-Ph-BPE–CuMes system, the steric hindrance is vital for the distribution of products and responsible for the stereoselectivity of this reaction. The steric hindrance between the phenyl ring of the two substrates and groups at the chiral centers in the ligand skeleton is identified as the original of the stereoselectivity for the titled reaction.

The stepwise hydrogenation of the C=C bond and C=O group of acrolein on Au₃ and Au₅ model systems is investigated using the density functional theory(DFT) PW91 functional. Our results show that the C=C hydrogenation is more favorable than that of C=O bond on Au₃ with the barriers of the rate-determining step being 0.35 and 0.62 eV respectively. On the other hand, the C=O reduction is preferred over the hydrogenation of the C=C bond on Au₅. The corresponding barriers of the rate-determining steps are 0.45 and 0.54 eV, respectively. This demonstrated that the second hydrogenation step controls the reaction on both Au₃ and Au₅ for C=O and C=C hydrogenation and the C=O hydrogenation on Au₅ is preferred over the hydrogenation of the C=C bond, which is helpful to address the reactivity of small size-selected supported gold clusters.

The in silico studies were performed in order to assess the binding affinity of selected organophosphorus compounds towards the acetylcholinesterase enzyme (AChE). Quantum mechanical calculations, molecular docking and molecular dynamics (MD) with molecular mechanics Generalized-Born surface area (MM/GBSA) were applied to assess quantitatively differences between the binding energies of acetylcholine (ACh; the natural agonist of AChE) and neurotoxic, synthetic correlatives (so-called “Novichoks”, and selected compounds from the G- and V-series). Several additional quantitative descriptors like root mean square fluctuation (RMSF) and the solvent accessible surface area (SASA) were briefly discussed to give – to the best of our knowledge – the first quantitative in silico description of AChE – Novichok non-covalent binding process and thus facilitate the search for an efficient and effective treatment for Novichok intoxication and in a broader sense - intoxication with other warfare nerve agents as well.

Molecular modeling studies were carried out at the DFT level of the adsorption of propane and propene on Ag surfaces as a model of the interaction of light hydrocarbons with Ag/ZrO2 catalysts for the catalytic combustion reaction. It was found that the most stable mode of adsorption of propene through its π system on Ag atom has energies consistent with chemisorption and generates an elongation of the C1=C2 bond, which would explain the increase in the activity of the catalysts as function of its metallic charge. The results obtained from the DFT calculations explain the different types of interaction between propene and propane with the metallic surface. The propene is chemisorbed on the Ag surface, distorting its bonds and generating its activation. This would imply that a higher metallic charge in the catalyst would increase the number of active sites in which this activation occurs, generating a higher activity. Besides, with the addition of O, the binding energy between the propene and the metal surface increased. On the other hand, the presence of a metallic surface is not enough for the activation of the propane molecule. This would explain why by increasing the amount of metal in the catalyst, the activity for the combustion of propane is practically not affected

Spin crossover (SCO) complexes are in the forefront of image, memory and sensing devices, with applications already established since for thirty years. In order to reach magnetic multistability conditions, the high-spin (HS) and low-spin (LS) states have to be carefully balanced by ligand field stabilization and spin pairing energies. Both of these effects could be effectively modelled by electronic structure theory, if the description would be accurate enough to describe these concurrent influences to within a few kJ/mol. Such a milestone would allow for the in silico-driven development of SCO complexes. However, so far, the ab initio simulation of such systems has been dominated by general gradient approximation density functional calculations. The latter can only provide the right answer for the wrong reasons, given that the LS states are grossly stabilized. In this contribution, we explore different venues for the parameterisation of hybrid functionals. A fitting set is provided on the basis of explicitly correlated coupled cluster calculations, with single- and multi-dimensional fitting approaches being tested to selected classes of hybrid functionals (hybrid, range separated and local hybrid). Promising agreement to benchmark data is found for a rescaled PBE0 hybrid functional and a local version thereof, with a discussion of different atomic exchange factors.

Mineral surfaces have been demonstrated to play a central role in prebiotic reaction, which are supposed to be at the basis of the origin of life. Among the various molecules proposed as precursors for these reactions, one of the most interesting is formamide. Formamide has been shown to be a pluripotent molecule, generating a wide distribution of relevant pre-biotic products. In particular, the outcomes of its reactivity are strongly related to the presence of mineral phases, acting as catalysts toward specific reaction pathways. Even if the mineral-products relationship has been deeply studied for a large pool of materials, the fundamental description of the formamide reactivity over the mineral surface at a microscopic level is missing in the literature. In particular, a key step of formamide chemistry at surfaces is its adsorption on the available interaction sites. This report aims to investigate the adsorption of formamide over a well-defined amorphous silica, chosen as model mineral surface. An experimental IR investigation of formamide adsorption has been carried out and its outcomes have been interpreted on the basis of first principles simulation of the process adopting a realistic model of the amorphous silica.

A series of (benzoimidazol-2-ylmethyl)amine palladium(II) complexes have been employed as catalysts in the homogenous hydrogenation of alkenes and alkynes under mild conditions. A correlation between the catalytic activity and the nature of the ligand was established. Kinetic studies of the hydrogenation reactions of styrene established pseudo-first-order dependence on styrene substrate. On the other hand, partial orders with respect to H2 and catalyst concentrations were obtained consistent with the formation of palladium(II) monohydride species as the active species. The nature of the solvent used influenced the hydrogenation reactions, where coordinating solvents resulted in lower catalytic activities. Density functional theory investigations provided valuable insights into the reactivity trends and influence of complex structure on the hydrogenation reactions.

Based on DFT (density functional theory) using B3LYP/6-31G method, theoretical investigations applied to demonstrate the structural, electronic properties and stability of (N,Nˊ-(1,4-phenylene)bis(1,8-naphthalimide)) is more stable than the compound (N-(4-amino phenyl)1,8-naphthalimide) by (-1.2762 eV or -29.4299 Kcal.mol-1) depending on the values of HOMO, synthesis reaction of imide is spontaneous and endothermic at temperature 275˚C according to the values of ∆rS, ∆rG and ∆rH.

Experimental studies of degradation of two ribonucleosides (guanosine and uridine) were carried out by making use of mechanochemistry. Mechanochemical experiments reveal the decomposition of guanosine and uridine promoted by nickel(II) and carbonate ions into guanine and uracil, respectively which were identified by HPLC and 1H NMR spectroscopy (this applied only to uracil). Additionally, DFT methodologies were used to probe the energetic viability of several degradation pathways, including in the presence of the same ions. Three mechanisms were analysed via ribose ring-opening: dry, single molecule water- and metal-assisted, which confirmed the mechanochemical degradation of ribonucleosides, with nucleobase preservation. These results can be applied to interpret the organic content of terrestrial and extra-terrestrial samples after mechanochemical treatment.

The theory of the continuous two-dimensional (2D) Fourier Transform in polar coordinates has been recently developed but no discrete counterpart exists to date. In the first part of this two-paper series, we proposed and evaluated the theory of the 2D discrete Fourier Transform (DFT) in polar coordinates. The theory of the actual manipulated quantities was shown, including the standard set of shift, modulation, multiplication, and convolution rules. In this second part of the series, we address the computational aspects of the 2D DFT in polar coordinates. Specifically, we demonstrate how the decomposition of the 2D DFT as a DFT, Discrete Hankel Transform (DHT) and inverse DFT sequence can be exploited for efficient code. We also demonstrate how the proposed 2D DFT can be used to approximate the continuous forward and inverse Fourier transform in polar coordinates in the same manner that the 1D DFT can be used to approximate its continuous counterpart.

The theory of the continuous two-dimensional (2D) Fourier Transform in polar coordinates has been recently developed but no discrete counterpart exists to date. In this paper, we propose and evaluate the theory of the 2D discrete Fourier Transform (DFT) in polar coordinates. This discrete theory is shown to arise from discretization schemes that have been previously employed with the 1D DFT and the discrete Hankel Transform (DHT). The proposed transform possesses orthogonality properties, which leads to invertibility of the transform. In the first part of this two-part paper, the theory of the actual manipulated quantities is shown, including the standard set of shift, modulation, multiplication, and convolution rules. Parseval and modified Parseval relationships are shown, depending on which choice of kernel is used. Similar to its continuous counterpart, the 2D DFT in polar coordinates is shown to consist of a 1D DFT, DHT and 1D inverse DFT.

The alkoxycarbonylation of styrene by palladium chloride is studied employing the density functional theory (DFT). Initially, [PdCl3]– reacts with methanol to form the methoxy-bound intermediate, which undergoes β-hydride elimination to form the key intermediate [PdCl2H]–. Then, a 1,2-insertion reaction to styrene takes place to form linear and branched alkyl coordinated with the PdII. Then CO coordination followed by a 1,1-insertion reaction leads to the formation of acyl intermediate. Next, the methanolysis leads to the formation of esters. Previous reports with other catalysts suggested the intermolecular/intramolecular transition state (TS) formation with a high activation barrier, and this step was the bottleneck. To the best of our knowledge, it is the first time we have considered a two-step mechanism for the alcoholysis of the ester formation mechanism. After coordination with the metal, the methanol undergoes oxidative addition to form the PdIV square pyramidal intermediate, followed by reductive elimination to form the ester with regeneration of the metal hydride active intermediate. Deeper insight into the nature of bonding at the TSs are obtained through energy decomposition with natural orbital for chemical valence (EDA-NOCV) and quantum theory of atoms in molecules (QTAIM).

In this review we explore the recent progress in catalytic materials for ammonia synthesis that are based on metal nitrides and other catalytic surfaces. It comprises a detailed overlook of various techniques used in ammonia synthesis research and the state-of-the-art modeling techniques employed to investigate new reaction mechanisms and more efficient processes for sustainable ammonia synthesis production. The review is discussed in the context of reaction mechanisms developed and recent progress that has been made with respect to thermal, electrochemical and photocatalytic ammonia synthesis.

In this research work, we examined the decomposition mechanisms of N-substituted diacetamides. We focused on the substituent effect on the nitrogen lone pair electron delocalization, withdrawing and electron donor groups. DFT functionals used included: B1LYP, B3PW91, CAMB3LYP, LC-BLYP, and X3LYP. Dispersion functions gd3bj were applied when necessary to improve non-covalent interactions in the transition state. Pople with higher angular moments and def2-TZVP basis sets were also applied and were crucial for obtaining consistent thermodynamic parameters. The proposed mechanism involves a six-membered transition state with the extraction of an α hydrogen. Several conformers of N-diacetamides were used to account for the decrease in entropy in the transition state in the rate-determining state. All calculations, including Natural Bond Orbital (NBO) analyses, were performed using the Gaussian16 computational package and its GaussView 6.0 visualizer, along with VMD and GNUPLOT software. The isosurfaces and IBSI indexes were calculated using MultiWFN and IGMPlot, respectively.

The high reactivity of acetylene group the formation of strong chemical bonds with active sites on mineral surfaces, thereby improving the flotation performance of gold minerals. This study utilized Density Functional Theory (DFT) to analyse the quantum chemical parameters of structure, Mulliken population, and the frontier orbitals of a thioester collector containing an acetylene group, PDEC (prop-2-yn-1-yl diethylcarbamodithioate). PDEC is compared with analogous thioester collectors Z-200 and Al-DECDT, and the interaction mechanism of PDEC on the Au(1 1 1) surface is simulated, followed by empirical validation through adsorption experiments. The findings indicate that S atom of PDEC in the carbon-sulfur group exhibit shorter covalent bond lengths, and reduced carbon-sulfur double bonds and Mulliken population, resulting in enhanced electron localization. This confers greater selectivity to PDEC during its adsorption on mineral surfaces. Frontier orbital analysis shows that the electrons of acetylene group possess a notable electron-accepting capacity, significantly influencing frontier orbital energy of PDEC and playing a pivotal role in the bonding interaction with mineral surfaces. Both the S atom in carbon-sulfur group and its acetylene group establish stable adsorption structures with the A(111) surface in a single coordination mode. The adsorption energy sequence is PDEC > Al-DECDT > Z-200. Partial density of states demonstrates that S 3p orbit of carbon-sulfur group hybridize with Au 5d orbit, while the C 2p orbit of the acetylene group engage in weaker back-donation bonding with Au 5d orbit. This is corroborated by electron density difference and post-adsorption Mulliken population analyses, revealing that S atom of carbon-sulfur group in PDEC donate electrons to Au atom, forming dominant positive coordination bonds, whereas the acetylene group accepts partial electrons from Au atom, resulting in weaker back-donation bonds. The adsorption experiments align with the DFT adsorption energy results.

The nature of the blue color in the iodine-starch reaction (or, in most cases, iodine-iodide-starch reaction, i.e. as I2 as well as I- are typically present) has for decades elicited debate. The intensity of the color suggests a clear charge-transfer nature of the band at ~600 nm, and there is consensus regarding the fact that the hydrophobic interior of the amylose helix is the location where iodine binds. Three types of possible sources of charge transfer have been proposed: (1) chains of neutral I2 molecules, (2) chains of poly-iodine anions (complicated by the complex speciation of the I2 - I- mixture), or (3) mixtures of I2 molecules and iodide or polyiodide anions. An extended literature review of the topic is provided here. According to the most recent data, the best candidate for the “blue complex” is a I2-I5-I2 unit – expected to occur in repetitive manner inside the amylose helix.

The molecular clusters ((HO)3Si-O-Si(OH)3, and (HO)3Al-O-Si(OH)3 ) representative of aluminosilicate mineral surface were employed to study the dissolution of aluminosilicate in acidic condition via density functional theory with the M06-2X+G(d,p) methodology. The surface termination sites (Si and Al) were both tetra-coordinated and the terminal oxygen was protonated in acidic condition. In the dissolution reaction, the calculated barrier height of the six-membered ring transition state complex containing two water molecules was predicted to be lower than that of four-membered ring transition state complex containing one water molecule. In addition, the calculated barrier heights for Al-terminated sites were predicted to be lower than those for the Si-terminated sites, suggesting that breaking the Al-O bond is easier than Si-O bond in the aluminosilicate mineral surface; the barrier heights of the surface termination sites with protonated terminal oxygen were lower than those without protonated terminal oxygen. With the fracture of Si-O and Al-O bonds, the Si and Al release from the aluminosilicate. These results confirm the experimental conclusions that the acidic condition facilitates the release of Si and Al from the aluminosilicate, and the concentration of Al leaching from aluminosilicate is higher than Si.

Structure based biological and chemical properties of 4-(carboxyamino)-benzoic acid has been studied by quantum chemical methods. The revamped geometric structure and its quantum chemical parameters were obtained by DFT-B3LYP/6-311G method. Normal mode analysis is performed to assign the fundamental vibrational frequencies as per the potential energy distribution (PED) by using the VEDA program. Simulation of IR and Raman spectral patterns are observed by refinement of scale factors. TD-DFT approach is used to explore the excited states of molecule and prediction of electronic absorption spectra. NMR chemical shifts of the molecule are determined by the gauge independent atomic orbital method. The molecular docking is performed to recognize the binding energy of the ligand with the dynamic site of protein. In our docking analysis, the protein 5DT6 shows the best results than other three proteins which could be used for further analysis. Further inter and intra molecular interactions, electrophilic, nucleophilic and chemical reactivity sites are found by molecular electrostatic potential, HOMO-LUMO and Global chemical reactivity descriptors. Thermodynamic property of the title compound is also reported. The determined quantum chemical parameters show high reactivity and the dipole moment was sufficiently high enough to induce nonlinear characteristics which are required for applications in optoelectronic devices.

Colorectal cancer is a major threat to the society causing the death through metastasis to several patients with stage IV. Computational tools provide a relatively quick procedure in order to evaluate several molecules for their drug activity. Prenylated flavonoids are well known for their anticancer properties even in colon cancer. Here, we provided altered structures of chalcones, based on theoretical studies that are showing better binding affinities to several colon cancer related proteins. Using molecular docking and dynamics, alongside with density function theory and ADMET studies we are representing two new derivatives of Xanthohumol prenylated flavonoids having promising results against this disease.

Density Functional Theory (DFT) full potential linearized augmented plane wave (FP-LAPW) method with the Modified Becke-Johnson (mBJ) approximation is used to perform spin polarised calculations of the transition metal perovskites MoScO₃ and WScO₃. Both depict half metallic behaviour with semiconducting and metallic in the minority and majority spins respectively. MoScO₃ and WScO₃ have indirect R− Γ band gaps in the minority spin channels of 3.61 and 3.82eV respectively. Moreover, they both show substantial magnetic moments of 2.99μ_B. In addition, we calculate the dielectric function, optical conductivity and the optical constants, namely, the refractive index, the reflectivity, the extinction and absorption coefficients.

Motivated by experiments, we undertake an investigation of electronic structure reconstruction and its link to electrodynamic responses of monoclinic MoO$_2$. Using a combination of LDA band structure with DMFT for the subspace defined by the physically most relevant Mo $4d$-bands, we unearth the importance of multi-orbital electron interactions to MoO$_2$ parent compound. Supported by a microscopic description of quantum capacity we identify the implications of many-particle orbital reconstruction to understanding and evaluating voltage-capacity profiles intrinsic to MoO$_2$ battery material. Therein, we underline the importance of the dielectric function and optical conductivity in the characterisation of existing and candidate battery materials.

In the upgrading of biomass pyrolysis vapors to hydrocarbons, dehydration accomplishes a primary objective of removing oxygen and acidic zeolites represent promising catalysts for dehydration reaction. Here, we utilize density functional theory calculations to estimate adsorption energetics and intrinsic kinetics of alcohol dehydration over H-ZSM-5, H-BEA, and H-AEL zeolites. ONIOM calculations of adsorption energies were observed to be inconsistent when benchmarked against QM/Hartree-Fock and periodic boundary condition calculations. However, reaction coordinate calculations of adsorbed species and transition states were consistent across all levels considered. Comparison of ethanol, iso-propanol (IPA), and tert-amyl alcohol (TAA) over these three zeolites allowed for a detailed examination of how confinement impacts reaction mechanisms and kinetics. TAA, seen to proceed via a carbocationic mechanism, was found to have the lowest activation barrier, followed by IPA and then ethanol, both of which dehydrate via a concerted mechanism. Barriers in H-BEA were consistently found to be lower than in H-ZSM-5 and H-AEL, attributed to late transition states and either elevated strain or inaccurately estimating long-range electrostatic interactions in H-AEL, respectively. Molecular dynamics simulations revealed that the diffusivity of these three alcohols in H-ZSM-5 are significantly overestimated by Knudsen diffusion, which will complicate experimental efforts to develop a kinetic model for catalytic fast pyrolysis.

Thermally-assisted-occupation density functional theory (TAO-DFT) has been an efficient electronic structure method for studying the ground-state properties of large electronic systems with multi-reference character over the past few years. To explore the time-dependent (TD) properties of electronic systems (e.g., subject to an intense laser pulse), in this work, we propose a real-time (RT) extension of TAO-DFT, denoted as RT-TAO-DFT. Besides, we employ RT-TAO-DFT to study the high-order harmonic generation (HHG) spectra and related TD properties of molecular hydrogen H2 at the equilibrium and stretched geometries, aligned along the polarization of an intense linearly polarized laser pulse. The TD properties obtained with RT-TAO-DFT are compared with those obtained with the widely used time-dependent Kohn-Sham (TDKS) method. In addition, issues related to the possible spin-symmetry breaking effects in the TD properties are discussed.

In this research, we utilize density functional theory (DFT) to study and investigate the adsorption process of methanol on three unique two-dimensional nanomaterials, namely BN, Graphene, and AlN. Eight sites for BN, AlN, and six sites for graphene were considered to reach full structural optimization. By conducting comprehensive simulations and analyses, we discovered diverse adsorption configurations and energy levels, which indicate different interaction strengths between methanol and the three 2D nanomaterials. Remarkably, AlN exhibits superior adsorption capabilities when compared to Graphene and BN which can be explained by attributable to the nature of charge transfer between the adsorbate and the adsorbent. For methanol adsorption on AlN, the strongest adsorption energy was (-0.5532 eV), and the amount of charge transferred from methanol to AlN was found to be (+0.075). For BN, the strongest adsorption energy was (-0.1351 eV), and the amount of charge transferred from methanol to BN was (+0.022). The density of states results indicated that the bandgap decreased, with a shift to the right. In contrast, for methanol adsorption on graphene, the strongest adsorption energy was found to be (-0.073 eV), and the amount of charge transferred from methanol to graphene was (+0.004). The density of states results showed no change in the bandgap. Our findings underscore the superiority of AlN’s potential over BN and Graphene for applications requiring efficient methanol adsorption, such as gas separation and storage technologies. This study emphasizes the superiority of AlN over Graphene and BN for tasks that necessitate effective methanol adsorption.

DFT calculations on the photoisomerization reactions of pyridazine N-oxide derivatives are presented. The irradiation of 3,6-diphenylpyridazine N-oxide allowed to obtain the first excited singlet state that underwent to a ring opening reaction induced to the oxygen migration to the adjacent carbon atom, with the formation of a diazo derivative. This intermediate can give a ring closure reaction to give a pyrazole derivative, or, with a higher transition energy, it can lose nitrogen allowing the formation of 2,5-diphenylfuran. The irradiation of 3-phenylpyridazine N-oxide allowed the formation only of 2-phenylfuran. In this case, calculations allowed to explain this behavior. The first excited singlet state gave a photoisomerization reaction with the formation of the corresponding diazo intermediate. This intermediate could not be converted into the corresponding pyrazole derivative because it was converted into a N-formyl pyrazole never reported in literature. The only possible reaction is the loss of nitrogen and the formation of 2-phenylfuran.

The conformations of trifluoroacetyl triflate, CF3C(O)OSO2CF3, were investigated through vibrational experimental methods (gas-phase FTIR, liquid-phase Raman, and Ar-matrix FTIR spectroscopy) and Density Functional Theory (DFT) calculations. A potential energy surface was computed using the B3P86 /6-31+g(d) approximation as a function of the dihedral angles τ1 = CCOS and τ2 = COSC. The surface reveals three minima, which were further optimized using the B3LYP method with various basis sets (6-31++G(d), 6-311++G(d), tzvp and cc-pvtz). The global minimum corresponds to a syn-anti conformer (the CO double bound syn with respect the O−S single bond and the C−O single bond anti with respect to de S−C single bond). The other two minima represent enantiomeric syn-gauche forms. The Ar-matrix FTIR spectrum exhibited clear evidence of the presence of two conformers. Furthermore, the randomization process observed following broad-band UV-visible irradiation facilitated the identification of the IR absorption of each conformer. Based on the Ar-matrix FTIR experiments, the vapour phase of trifluoroacetyl triflate at room temperatures was composed of approximately 60-70% of the syn-anti conformer and 30-40% of the syn-gauche form.

African indigenous herbs and medicinal plants are extensively reported for their protective and therapeutic potential against Diabetes. However, most of the constituent phytochemicals that may account for the therapeutic activity are largely uninvestigated. Exploring novel phytochemical–target interactions in silico could help to provide useful insights into the mechanism underpinning the biological activities of these plants and their constituent phytochemicals. The aim of this study was to explore the interactions of terpene struc-tures previously reported from selected African antidiabetic with two emerging drug targets in diabetes. Structure-based virtual screening was used to screen 107 terpene structures against DPP-4 and PTP1B enzymes. The MD simulation, MM-GBSA free energy calculation and DFT were used to clarify the inter-actions of the in silico hits with the target enzymes. Molecular docking, post-docking Prime MM-GBSA analysis revealed the top terpenes with high binding affinity with the active site regions of DPP-4 and PTP1B. Ensemble docking revealed three triterpenes viz: cucurbitacin B (T1), 6-Oxoisoiguesterin (T4) and 20-Epi-isoiguesterinol (T2) as in silico hits which exhibit strong interaction potential with critical residues that define the catalytic triad (Ser630 and His740); oxyanion cavity (Ser631); hydrophobic S1 pocket (Tyr662) and the charged S2 pocket (Arg125) in the active site region of DPP-4. The interactions of these compounds with DPP-4 exhibited structural stability and conformational flexibility during 100 ns full atomistic MD simulation as indicated by the structure dynamics parameters including RMSD, RoG, SASA and hydrogen bond number. The post-MD MM/GBSA calculations further revealed the stability of the triterpene-DPP-4 complexes. Furthermore, Frontier molecular orbital calculations showed that, the triterpenes possess high interaction potential with the enzyme. The triterpenes showed desirable ADMET properties and drug-likeness. Therefore, cucurbitacin B, 6-Oxoisoiguesterin and 20-Epi-isoiguesterinol are recommended for experimental validation.

The cohesive energy of transition metal nanoparticles is crucial to understanding their stability and fundamental properties, which are essential for developing new technologies and applications in fields such as catalysis, electronics, energy storage, and biomedical engineering. In this study, we systematically investigate the size-dependent cohesive energies of all the 3d, 4d, and 5d transition-metal nanoparticles using first-principles density functional theory calculations. Our results show that the cohesive energies of nanoparticles decrease with decreasing size due to the increased surface-to-volume ratio and quantum confinement effects. We also find that the size-dependent cohesive energy trends are different for different transition metals, with some metals exhibiting stronger size effects than others. Our findings provide insights into the fundamental properties of transition-metal nanoparticles and have potential implications for their applications in various fields such as catalysis, electronics, and biomedical engineering.

Nanoporous carbons were prepared by chemical and physical activation from mangosteen peel-derived chars. The removal of atrazine was studied due to the bifunctionality of the N-groups. Pseudo-first-order, pseudo-second order and intraparticle pore diffusion kinetic models were analyzed. Adsorption isotherms were also analyzed according to Langmuir and Freundlich models. Results obtained were compared against two commercial activated carbons with comparable surface chemistry and porosimetry. The highest uptake was found for the carbons with higher content of basic surface groups. The role of the oxygen-containing groups on the removal of atrazine was estimated experimentally by the surface density. Results were compared with the adsorption energy of atrazine theoretically estimated on pristine and functionalized graphene with different oxygen-groups using periodic DFT methods. The energy of adsorption follows the same trend observed experimentally, namely the more basic the pH the more favored is the adsorption of atrazine. Micropores play an important role in the uptake of atrazine at low concentration but the presence of mesoporous is also required to inhibit the pore mass diffusion limitations. The present work contributes to the understanding of the interactions between triazine-based pollutants and the surface functional groups on nanoporous carbons in the liquid-solid interface.

For the ground-state properties of gas-phase nanomolecules with multi-reference character, thermally-assisted-occupation density functional theory (TAO-DFT) has been recently found to outperform the widely used Kohn-Sham density functional theory, when the conventional exchange-correlation energy functionals are employed. Aiming to explore solvation effects on the ground-state properties of nanomolecules with multi-reference character at a minimal computational cost, we combine TAO-DFT with the polarizable continuum model (PCM). To show its usefulness, TAO-DFT-based PCM (TAO-PCM) is employed to study the electronic properties of linear acenes in three different solvents (toluene, chlorobenzene, and water). According to TAO-PCM, in the presence of these solvents, the smaller acenes should have nonradical nature, and the larger acenes should have increasing polyradical nature, showing remarkable similarities to the past findings in the gas phase.

Cadmium (II) contamination in the environment is an emerging problem due to its acute toxicity and mobility, so it is very urgent to remove this species from industrial wastewater before it is discharged into the environment. Thus, a starch-based activated carbon (AC) with a specific surface area of 1600 m2g-1 is used as an adsorbent for the capturing of toxic Cadmium (II) ions from synthetic solution. The sorbent is characterized by BET, SEM, TEM, XRD, FT-IR, TGA, and zeta potential. The maximum uptake (284 mg g-1) of Cadmium (II) ion is obtained at pH 6. The thermodynamics parameters like ∆G, ∆H, ΔS are found to be -17.42 kJmol-1, 6.49 kJ mol-1, and 55.66 Jmol-1K-1 respectively, revealing that the adsorption mechanism is endothermic, spontaneous, and feasible. The experimental data follows the D-R and Langmuir models well. The mass transfer is controlled by pseudo 2nd order kinetics. Furthermore, the density functional theory simulations demonstrate that the activated carbon strongly interacted with the Cd (II) ion through its various active sites. The adsorption energy noted for all interactive sites is highly negative (-0.45 eV to -10.03 eV), which shows that the adsorption process is spontaneous and stable which is in agreement with the experimental thermodynamics analysis.

Hydrogenated small fullerenes (Cn, n<60) are of interest as potential astrochemical species, and as intermediates in hydrogen catalysed fullerene growth. However computational identification of key stable species is difficult due to the vast combinatorial space of structures. In this study we explore routes to predict stable hydrogenated small fullerenes. We show that neither local fullerene geometry nor local electronic structure analysis are able to correctly predict subsequent low energy hydrogenation sites, and indeed sequential stable addition searches also sometimes fail to identify most stable hydrogenated fullerene isomers. Of the empirical and semi-empirical methods tested, GFN2-xTB consistently gives highly accurate energy correlation (r>0.99) to full DFT-LDA calculations at a fraction of the computational cost. This allows identification of the most stable hydrogenated fullerenes up to 4H for four fullerenes, namely two isomers of C28 and C40, via “brute force” systematic testing of all symmetry inequivalent combinations. The approach shows promise for wider systematic studies of smaller hydrogenated fullerenes.

The unfolded band structure and optical properties of Cu-doped KCl crystals were computed by first principles within the framework of density functional theory, implemented in the ABINIT electronic structure package utilizing pseudopotential approximation and a plane-wave basis set. From a theoretical point of view, Cu substitution into pristine KCl crystals requires calculation by the supercell (SC) method. This procedure shrinks the Brillouin zone, resulting in a folded band structure that is difficult to interpret. To solve this problem and gain insight into the effect of copper ions (Cu+) on electronic properties, the band structure of SC KCl:Cu was unfolded to make a direct comparison with the band structure of the primitive cell (PC) of pristine KCl. To understand the effect of Cu substitution on optical absorption, we calculated the imaginary part of the dielectric function of KCl:Cu through a sum-over-states formalism and broke it down into different band contributions by partially making an iterated cumulative sum (ICS) of selected valence and conduction bands. Consequently, we identified those interband transitions that give rise to the absorption peaks due to the Cu+ ion. These transitions involve valence and conduction bands formed by the Cu-3d and Cu-4s electronic states

Aurora kinase A (AURKA) is a normal cell proliferation-inducing enzyme encoded by AURKA gene, with over-expression observed in different types of malignancies. Hence, the goal is to find potential inhibitors against AURKA. In this study, molecular docking, Standard Precision and Extra Precision methods were employed. After the docking study, the ligands showed an extremely low binding score which suggested very high binding affinity of the ligands. Furthermore, Quantum polarized ligand docking (QPLD) was performed to predict the binding status of the molecules. Based on the binding affinity, the top four compounds were chosen for further analysis. The docked complexes were further analyzed in explicit water conditions using 100 ns molecular dynamics simulations and binding free energy calculation. Then, density functional theory (DFT) calculation was used to calculate the molecular properties of the molecules. Finally, systems biology experiments validated the molecular docking and molecular dynamics simulation studies and indicated that quercetin, kaempferol, luteolin and rutin could inhibit the AURKA. The results show that, these four molecules have high binding affinity to the AURKA and significant interactions (LEU139, GLU211and ALA213) were also identified with the hinge region of Aurora kinase A. Thus, LEU139, GLU211, and ALA213 were identified as the crucial protein mechanisms.

We report the electronic, magnetic and transport properties of a prototypical antiferromagnetic (AFM) spintronic device. We chose Cr as the active layer because it is the only room-temperature AFM elemental metal. We sandwiched Cr between two non-magnetic metals (Pt or Au) with large spin-orbit coupling. We also inserted a buffer layer of insulating MgO to mimic the structure and finite resistivity of a real device. We found that, while spin-orbit has a negligible effect on the current flowing through the device, the MgO layer plays a crucial role. Its effect is to decouple the Cr magnetic moment from Pt (or Au) and to develop an overall spin magnetization. We have also calculated the spin-polarized ballistic conductance of the device within the Büttiker-Landauer framework, and we have found that for small applied bias our Pt/Cr/MgO/Pt device presents a spin polarization of the current amounting to ~25%.

1-[(4-ethyl-2-phenyl-4,5-dihydro-1,3-oxazol-4-yl)methyl]-4-phenyl-1H-1,2,3-triazole (Ph4) and1-[(4-ethyl-2-phenyl-4,5-dihydro-1,3-oxazol-4-yl)methyl]-5-phenyl-1H-1,2,3-triazole (Ph5) are new isomers of the triazole derivative family, were synthesized and tested on the corrosion of mild steel in molar hydrochloric acid molar media using weight loss, electrochemical polarization and impedance spectroscopy. Then the experimental results were confirmed by quantum chemical calculations using DFT at B3LYP /6-31G (d,p). The compound Ph4 is the best inhibitor and its inhibitory efficiency increased with increasing concentration and reaching 95% at 10⁻³ M. Polarization curves studies show that both compounds tested are mixed-type inhibitors. Nyquist curves presented a single capacitive loop, their diameter increases progressively with both inhibitors concentration. The change of the substitution phenyl from position 5 to position 4 in the triazole ring increases the inhibitory effect of the triazole compounds. The effect of temperature on the corrosion behavior of iron indicates that the inhibitory efficiency of the two inhibitors decreases with increasing temperature in the range of 308 to 338K. DFT study is in good correlationwith the experimental results.

The emission of toxic gases from industrial production have intensified issues related to atmospheric pollution and human health. Consequently, the effective real-time monitoring and removal of these harmful industrial gases have emerged as significant challenges. In this work, the density functional theory (DFT) method was utilized to examine the adsorption behaviors and electrical characteristics of Ni-decorated InSe (Ni-InSe) monolayer when interacting with twelve gases (CO, NO, NO2, NH3, SO2, H2S, H2O, CO2, CH4, H2, O2 and N2). A comparative assessment of adsorption strength and sensing properties was performed through analyses of electronic structure, work function and recovery time. The results show that Ni doping enhances the electrical conductivity of the InSe monolayer and improves the adsorption capabilities for six toxic gases (CO, NO, NO2, NH3, SO2, H2S). Furthermore, the adsorption of these gases on the Ni-InSe surface is characterized as chemisorption, as indicated by the analysis of adsorption energy, density of states, and charge density difference. Additionally, the adsorption of CO, NO, NO2, and SO2 results in significant alterations to the bandgap of Ni-InSe, with changes of 18.65%, 11.37%, 10.62%, and –31.77%, respectively, underscoring its exceptional sensitivity. Moreover, the Ni-InSe monolayer exhibit moderate recovery times of 3.24 s and 22.72 s at 298 K for the SO2 and H2S, respectively. Consequently, the Ni-InSe is regarded as a promising gas sensor for detecting SO2 and H2S at room temperature. This research establishes a foundation for developing Ni-InSe based gas sensor in detecting and mitigating harmful gas emissions.

Recently, oriented external electric fields (OEEFs) have earned much attention due to the possibility of tuning the properties of electronic systems. From a theoretical perspective, one can resort to electronic structure calculations to understand how the direction and strength of OEEFs affect the properties of electronic systems. However, for multi-reference (MR) systems, calculations employing the popular Kohn-Sham density functional theory with the traditional semilocal and hybrid exchange-correlation energy functionals can yield erroneous results. Owing to its decent compromise between accuracy and efficiency for MR systems at the nanoscale (i.e., MR nanosystems), in this study, thermally-assisted-occupation density functional theory (TAO-DFT) is adopted to explore the electronic properties of n-acenes (n = 2--10), containing n linearly fused benzene rings, in OEEFs, where the OEEFs of various electric field strengths are applied along the long axes of n-acenes. According to our TAO-DFT calculations, the ground states of n-acenes in OEEFs are singlets for all the cases examined. The effect of OEEFs is shown to be significant on the vertical ionization potentials and vertical electron affinities of ground-state n-acenes with odd-number fused benzene rings. Moreover, the MR character of ground-state n-acenes in OEEFs increases with the increase of the acene length and/or the electric field strength.

The reaction between cadmium nitrate tetrahydrate and N,N'-bis(pyridin-3-ylmethyl)oxalamide (L) in 1:3 molar ratio in water/acetonitrile (1:6 v/v) mixture afforded single crystals of compound 1 suitable for X-ray diffraction analysis. Compound 1 consists of the coordination polymer (CP) [[Cd(L)2(H2O)2](NO3)2·4H2O]∞, in which CdII ions are bridged by the neutral L antiperiplanar N-ligands in a wavy ribbon fashion developing along the c-axis. Two trans-disposed water molecules complete the pseudo-octahedral coordination geometry of the metal ion. The crystal packing of 1 revealed the interplay between π-π stacking interactions and an intricate hydrogen-bonded network involving oxalamides, nitrates and water molecules. The donor properties of L and the intermolecular interactions in compound 1 are interpreted based on hybrid-DFT calculations.

Due to its large hole mobility, Organic Rubrene (C42H28) has attracted research questions on its applications in electronic devices. In this work, extensive first-principles calculations were made to predict some temperature and doping dependent properties of Organic Semi- conductor Rubrene. We use Density Functional Theory (DFT) to investigate the electronic structure, elastic and transport properties of the Orthorhombic phase of the Rubrene compound. The calcu- lated band structure shows the Orthorhombic phase has a direct bandgap of 1.26 eV. From the Vickers hardness (1.080 GPa), our calculations show that Orthorhombic Rubrene is not a super hard material and can find useful application as a flexible semicon- ductor. The calculated transport Inverse Effective Mass and Elec- tronic Fitness Function show that the Orthorhombic Rubrene Crystal Structure is a p-type thermoelectric material at high temperatures.

Two new coordination compounds of Mn(II) and Cu(II) viz. [Mn(bz)2(Hdmpz)2(H2O)] (1) and [Cu(crot)2(Hdmpz)2] (2) (where, bz = benzoate, crot = crotonate, Hdmpz = 3, 5-dimethyl pyrazole) have been synthesized and characterized using single crystal X-ray diffraction technique, FT-IR, electronic spectroscopy, TGA and elemental analyses. Compounds 1 and 2 crystallize as mono-nuclear coordination compounds of Hdmpz based penta-coordinated Mn(II) and hexa-coordinated Cu(II) respectively containing distorted trigonal bipyramidal and distorted octahedral geome-tries. Crystal structure analysis of compound 1 reveals the presence C‒H⋯π and π-stacking in-teractions along with O‒H⋯O, N‒H⋯O and C‒H⋯O H-bonding interactions which stabilizes the layered assembly of the compound. Similarly, the presence of hydrogen bonding along with π-stacking interactions stabilizes the crystal structure of compound 2. We have carried out theo-retical investigations to analyze π⋯π H-bonding and antiparallel CH···π non-covalent interac-tions observed in the compounds. DFT calculations were performed to evaluate strength of these interactions energetically. Moreover, QTAIM and non-covalent interaction (NCI) plot index computational tool were used to characterize them and evaluate the contribution of the H-bonds.

Currently, the chemistry of conjugated nitrodienes is becoming more and more popular. These molecules are successfully applied in cycloaddition to synthesize six-membered rings in Diels-Alder reactions. Nitrodienes can be also applied to obtain bis-compounds in [3+2] cycloaddition. Moreover, the presence of a nitro group in the structure provides a possibility of further modification of the products. The simplest symmetrical representative of conjugated nitrodienes is (1E,3E)-1,4-dinitro-1,3-butadiene. Although the first mentions of the compound date back to the early 1950s, the compound has not yet been examined thoroughly enough. Therefore, in this article a comprehensive study of (1E,3E)-1,4-dinitro-1,3-butadiene has been described. For this purpose, an experimental study including synthesis process as well as spectral characteristic has been conducted. So as to better understand the properties of this compound a computational study of reactivity indices based on MEDT and also assessment of pharmacokinetics and biological activity according to ADME and PASS methodologies have been made. On this basis, some future application trends of (1E,3E)-1,4-dinitro-1,3-butadiene have been proposed.

Reactions in water between the Cu2(µ-EGTA) chelate (EGTA = ethylene-bis(oxyethyleneimino)tetraacetate(4-) ion) and 2,6-diaminopurine (Hdap) in molar ratios 1:1 and 1:2 yield only blue crystals of the ternary compound [Cu4(μ-EGTA)2(μ-H(N3)dap)2(H2O)2]·7H2O (1) that has been studied by single crystal X-ray diffractometry, various physical methods (thermal stability, spectral and magnetic properties), as well as DFT theoretical calculations. In the crystal, uncoordinated water is disordered. The tetranuclear complex molecule also has some irrelevant disorder in an EGTA-ethylene moiety. In the complex molecule, both bridging organic molecules act as binucleating ligands. There are two distorted five- (type 4+1) and two six- (type 4+1+1) Cu(II) centres. Each half EGTA acts as a tripodal tetradentate Cu(II) chelator, with mer-NO2+O(ether, distal) conformation. Hdap exhibits the tautomer H(N3)dap, with the dissociable H-atom on its less basic N-heterocyclic atom. These features favour the efficient cooperation between Cu-N7 or Cu-N9 bonds with appropriate O-EGTA atoms, as N6-H···O or N3-H···O interligand interactions respectively. Bridging role of both organics determines the tetranuclear dimensionality of the complex in 1. In this crystal, such molecules associate in zig-zag chains, built by alternating ,-interactions between the five- or six-atom rings of Hdap ligands of adjacent molecules. DFT theoretical calculations (using two different theoretical models and characterized by the quantum theory of “atoms in molecules”) reveal the importance of these ,-interactions between Hdap ligands, as well as that corresponding to the referred hydrogen bonds in the contributed tetranuclear molecule.

We present the results of a twofold experimental and computational study of (0001) GaN/AlN multilayers forming pseudomorphic superlattices. High-Resolution Transmission Electron Microscopy (HRTEM) shows that heterostructures with GaN Quantum Wells (QW) four c-lattice parameters thick are misfit-dislocation free. Accurate structural data are extracted from HRTEM images via a new methodology optimizing the residual elastic energy stored in the samples. Total energy calculations are performed with several models analogous to the experimental QWs with increasing thicknesses of GaN, whereas this of the AlN barrier is kept fixed at n=8 c-lattice parameters. With vanishing external stresses, minimum energy configurations of the studied systems correspond to different strain states. Linear elasticity accurately yields the corresponding lattice parameters, suppressing the need for on-purpose total energy calculations. Theoretically justified parabolic fits of the excess interfacial energy yield the values of interfacial stress and elastic stiffness as functions of the GaN QW thickness. Total species-projected densities of states and gap values extracted therefrom allow deciphering the effect of the evolving strain on the electronic structure of the superlattice. It is found that the gap energy decreases linearly with increasing the strain of the QW. These results are briefly discussed in the light shed by previous works from the literature.

In the present work we have investigated an organic semiconductor based on tris(8-hydroxyquinoline) aluminum (AlQ3) doped with tetracyanoquinodimethane (TCNQ), which can be used as a photoactive layer in organic light-emitting device (OLED). DFT calculations were carried out to optimize the structure of semiconductor species and get related constants in order to compare experimental and theoretical results. The semiconductor AlQ3-TCNQ was structurally characterized and their experimental IR spectrum was compared with that obtained through DFT calculations. Subsequently, AlQ3-TCNQ films with polypyrrole (PPy) matrix were fabricated, they were morphologically and mechanically characterized by Scanning Electron and Atomic Force Microscopy techniques. The maximum stress for the film is 8.66 MPa and the Knoop hardness is 0.0311. The film was analyzed in its optical behavior and the optical properties of hybrid film were found to exhibit two indirect allowed transitions at 2.64 and 3.44 eV. Finally, an OLED type was fabricated that was electrically characterized. Applying a cubic-spline approximation to fit cubic polynomials to the J-V curves, the ohmic to SCLC transition voltage VON and the trap-filled-limit voltage VTFL for the device were obtained. Then, the free carrier density and trap density for the device were approximated to n0=2.4787×10171m3 and Nt=1.7419×10291m3 respectively.

Diethyldithiocarbamate (DDTC) has been employed in the sulfide ore flotation process, due to its excellent collection performance. Herein, we investigated the interfacial adsorption behavior of DDTC on four mineral phases of high-sulfur residue — sulfur, pyrite, sphalerite and lead sulfate. The adsorption behavior — adsorption structure and energy and electron localization function cross section — of DDTC and H2O were explored using density function theory calculation. The result was helpful to construct a co-adsorption model of DDTC and H2O, which was validated by the pure minerals flotation operation and the characterization of fourier transform infrared spectra. The co-adsorption model indicated that the DDTC adsorption on the sulfur, sphalerite and lead sulfate was weak with physical bonding, while its adsorption on the pyrite was strong with chemical bonding. Practical bench-scale operation of high-sulfur residue flotation was performed, whose result was different from that obtained from the pure mineral flotation. To explain the difference, our developed model predictions and the mineral fugacity pattern analysis on the high-sulfur residue flotation were synergistically used. Overall, this work first proposed the co-adsorption model of DDTC and H2O and provided important insights into the interfacial adsorption in the high-sulfur residue flotation.

Controlling and understanding Cu-catalyzed homocoupling reaction is crucial to prompt the development of efficient Cu-catalyzed cross-coupling reactions. The presence of a coordinating base (hydroxide, methoxide) enables the B-to-Cu(II) transmetalation from aryl boronic acid to CuIICl2 in methanol, through formation of a mixed Cu-(μ-OH)-B intermediates. A second B-to-Cu transmetalation to form bis-aryl Cu(II) complexes is disfavored. Instead, organocopper(II) dimers undergo a coupled transmetalation-electron-transfer (TET) allowing the formation of a bis-organocopper(III) complexes readily promoting reductive elimination. Based on this mechanism some guidelines are suggested to control the undesired formation of homocoupling product in Cu-catalyzed cross-coupling reactions.

The structural, elastic, anisotropic elastic, electronic, vibrational and properties of the Perovskite type Hydrides RbXH3 (X = Be, Ca, Mg) were performed via Vienna Ab – initio Simulation Pac-kage (VASP) based on Density Functional Theory (DFT). Our results have exhibited a well-agreement with previous calculations and experiments for each compound. In order to de-termine physical properties of RbXH3 has been used the Generalized Gradient Approximation (GGA) with Perdew-Burke-Ernzerhof (PBE) functional at this study. Present compounds were found to be mechanically stable as well as their gravimetric hydrogen storage capacities has been investigated. The Perovskite type Hydrides RbBeH3 and RbMgH3 has an indirect bandgap of 0.274 eV and 2.209 eV while RbCaH3 has a direct bandgap of 3.274 eV respectively and therefo-re these compounds has shown a semiconductor behaviour at equilibrium. Besides directional dependence of anisotropic properties was visualized by representing them with maximum - mi-nimum points..

Cadmium(II) contamination in the environment is an emerging problem due to its acute toxicity and mobility, so it is very urgent to remove this species from industrial wastewater before it is discharged into the environment. Thus, a starch-based activated carbon (AC) with a specific surface area of 1600 m2g-1 is used as an adsorbent for the capturing of toxic cadmium(II) ions from synthetic solutions. The sorbent is characterized by BET, SEM, TEM, XRD, FT-IR, TGA, and zeta potential. The maximum uptake (284 mg g-1) of Cadmium(II) ion is obtained at pH 6. The thermodynamic parameters like ∆G, ∆H, ΔS are found to be -17.42 kJmol-1, 6.49 kJ mol-1, and 55.66 Jmol-1K-1 respectively, revealing that the adsorption mechanism is endothermic, spontaneous, and feasible. The experimental data follows the D-R and Langmuir models well. The mass transfer is controlled by pseudo 2nd order kinetics. Furthermore, the density functional theory simulations demonstrate that the activated carbon strongly interacted with the Cd(II) ion through its various active sites. The adsorption energy noted for all interactive sites is highly negative (-0.45 eV to -10.03 eV), which shows that the adsorption process is spontaneous and stable which is in agreement with the experimental thermodynamics analysis.

An ability of different molecular potentials to reproduce the properties of 2D molybdenum disulphide polymorphs is examined. Structural and mechanical properties, as well as phonon dispersion of the 2H, 1T and 1T’ single-layer MoS2 (SL MoS2) phases, were obtained using density functional theory (DFT) and molecular statics calculations (MS) with Stillinger-Weber, REBO, SNAP, and ReaxFF interatomic potentials. Quantitative systematic comparison and discussion of the results obtained are reported.

Since the discovery of the aggregation-induced emission effect in 2001, diaminodicyanoquinone derivatives (DADQs) have presented interesting fluorescence properties, allowing them to be considered fluorescent dyes capable of showing quantum yields above 90%. Besides, the diaminodiacyanoquinone core represents a versatile building block propense either to modification or integration into different systems to obtain and provide them unique photophysical features. Herein, we carried out a theoretical study on the fluorescence properties of three different diaminodicyanoquinodimethane systems. Therefore, time-dependent density functional theory (TD-DFT) was used to obtain the values associated with the dipole moments, oscillator strengths, and the conformational energies between the ground and the first excited states of each molecule. The results suggest that only two of the three studied systems possess significant luminescent properties. In a further stage, the theoretical insights were confirmed by means of experimental measurements, which not only retrieved the luminescence of the DADQs, but also suggest a preliminary and promising antibacterial activity of these systems.

A Zn(II) perchlorate complex has been prepared and characterized by single X-ray crystallography, nuclear magnetic resonance spectroscopy, thermogravimetric analysis, infrared spectroscopy, elemental analysis, and UV-vis spectroscopy. The complex crystallizes in the monoclinic space group P21/c (Z = 4) with a pentacoordinated zinc center. Interestingly, the Zn complex was found be to a potential fluorophore that could sense acetone and other ketones with high selectivity and sensitivity.

The reaction mechanism of the carboxylation of K-2-naphthoxide was investigated by density functional theory calculations and spectroscopic studies. The reaction intermediates and products were confirmed by CO₂ adsorbed-FTIR and ¹H-NMR measurements. Four steps of the reaction pathway were identified: CO₂ activation, electrophilic substitution, CO₂-K complex rearrangement, and H-shift, producing 2-hydroxy-1-naphthoic acid (2,1-HNA), 2-hydroxy-3-naphthoic acid (2,3-HNA), and 2-hydroxy-6-naphthoic acid (2,6-HNA). The occurrence of CO₂-K complex rearrangement was also confirmed. These energy profiles of reaction pathways for the reaction intermediates were well consistent the experimental results on the carboxylation of K-2-naphthoxide.

Novel high energy density materials N14 (1,6-dihydro-1,2,3,3a,4,5,5a,6,7,8,8a,9,10,10a-tetradecazapyrene) and N18 (1,2,2a,3,4,4a,5,6,6a,7,8,8a,9,10,10a,11,12a-octadecazacoronene) were designed, and their structures, detonation performance and stabilities were calculated employing density functional theory (DFT). Calculations reveals that they have a good balance between high energy and stability. Their energy gaps between LUMO and HOMO are all lower than that of TATB, while their impact sensitivity h_50% is estimated close to that of RDX. Concerning energy, detonation performance of the N14 (P = 43.6 GPa, D = 10040 m/s, Q = 2214 cal/g) and the N18 (P = 37.4 GPa, D = 9400 m/s, Q = 2114 cal/g) are comparable to CL-20.

To make low-cost catalytic materials that mimic the activity of tyrosinase enzymes (Catechol oxidase) is an exciting challenge of biochemical technology. Herein, we report the synthesis of a series of acylhydrazone-pyrazoles based biomolecule materials (L1-L7) with superior catecholase activity. These biomolecules were synthesized by a one pot chemical condensation between 5-methyl-1H-pyrazole-3-carbohydrazide and benzaldehyde derivatives. The X-ray single crystal diffraction (XRD) for two ligands L1 and L2 have been studied and the molecular structures were optimized and confirmed using the density functional theory (DFT/B3LYP) method. Copper (II) complexes of the biomolecules (L1-L7), generated in-situ, and were studied for their catalytic activities towards the oxidation reaction of catechol to ortho-quinone according to two parameters: the nature of the ligand and the nature of counter anion. The L7-CuSO4 was found to have an excellent catalytic activity (105.42 μmol·L−1·min−1) among the catalysts recently reported in the existing literature.

In this paper, the synthesis of two novel luminescent Eu3+ ion complexes [Eu(TFT)3(phen) (1) and Eu(TFT)3(bpy)•Hex (2)] based on the combination of 2-(2,2,2-trifluoroethyl)-1-tetralone (TFT), containing n-donor ligands (1,10-phenanthroline or 2,2'-Bipyridine) and Eu3+ ion is reported herein, and their structural features are discussed on the basis of X-ray crystallographic and thermal analyses. We observed that the ligands transfer energy effectively to the metal center by fluorescence, IR and UV spectrograms studies. The structures and properties of complexes 1-2 were optimized by the DFT theoretical calculation, and the calculation results were consistent with the experimental X-ray structure data and spectral analysis.

Two new Mn(II) and Zn(II) metal-organic compounds of 1,10-phenanthroline and methyl benzoates viz. [Mn(phen)2Cl2]2-ClBzH (1) and [Zn(4-MeBz)2(2-AmPy)2] (2) (where, 4-MeBz = 4-methylbenzoate, 2-AmPy = 2-aminopyridine, phen = 1,10-phenanthroline, 2-ClBzH = 2-chlorobenzoic acid) have been synthesized and characterized using elemental analysis, TGA, spectroscopic (FTIR, electronic) and single crystal X-ray diffraction techniques. Crystal structure analysis of the compounds reveals the presence of various non-covalent interactions which provides stability to the crystal structures. Crystal structure analysis of the compound 1 reveals the formation of supramolecular dimer of 2-ClBzH enclathrated within the hexameric host cavity formed by the neighboring monomeric units. Compound 2 is a mononuclear compound of Zn(II) where flexible binding topologies of 4-CH3Bz is observed with the metal centre. Moreover various non-covalent interactions such as lp(O)-π, lp(Cl)-π, C‒H∙∙∙Cl, π-stacking interactions as well as N‒H∙∙∙O, C‒H∙∙∙O and C‒H∙∙∙π hydrogen bonding interactions are found to be involved in plateauing the molecular self-association of the compounds. The remarkable enclathration of the H-bonded 2-ClBzH dimer into a supramolecular cavity formed by two [Mn(phen)2Cl2] complexes has been further studied theoretically using density functional theory (DFT) calculations, non-covalent interaction (NCI) plot index and quantum theory of atoms in molecules (QTAIM) computational tools. Synergistic effects have been also analysed using molecular electrostatic potential (MEP) surface analysis.

A series of polynuclear, dinuclear, and mononuclear Mo(VI) complexes were synthesized with the hydrazonato ligands derived from 5-methoxysalicylaldehyde and the corresponding hydrazides (isonicotinic hydrazide (H2L1), nicotinic hydrazide (H2L2), 2-aminobenzhydrazide (H2L3) or 4-aminobenzhydrazide (H2L4)). The metallosupramolecular compounds obtained from non-coordinating solvents, [MoO2(L1,2)]n (1 and 2) and [MoO2(L3,4)]2 (3 and 4), formed infinite structures and metallacycles, respectively. By blocking two coordination sites with cis-dioxo ligands, the molybdenum centers have three coordination sites occupied by the ONO donor atoms from the rigid hydrazone ligands and one by N atom of pyridyl or amine-functionalized ligand subcomponents from the neighbouring Mo building units. The reaction in methanol afforded the mononuclear analogues [MoO2(L1-4)(MeOH)] (1a-4a) with additional monodentate MeOH ligand. All isolated complexes were tested as catalysts for cyclooctene epoxidation using tBuOOH (TBHP) as an oxidant in water. The impact of the structure and ligand lability on the catalytic efficiency in homogeneous cyclooctene epoxidation was elucidated through theoretical considerations. Thus, dinuclear assemblies exhibited better catalytic activity than mononuclear or polynuclear complexes.

In this computational study, we investigate the electronic properties of zigzag graphene nano-parallelograms (GNPs), which are parallelogram-shaped graphene nanoribbons of various widths and lengths, using thermally-assisted-occupation density functional theory (TAO-DFT). Our calculations reveal a monotonic decrease in the singlet-triplet energy gap as the GNP length increases. The GNPs possess singlet ground states for all the cases examined. With the increase of GNP length, the vertical ionization potential and fundamental gap decrease monotonically, while the vertical electron affinity increases monotonically. Besides, as the GNP length increases, the symmetrized von Neumann entropy increases monotonically, denoting an increase in the degree of multi-reference character associated with ground-state GNPs. The occupation numbers and real-space representation of active orbitals indicate that there is a transition from the nonradical nature of the shorter GNPs to the increasing polyradical nature of the longer GNPs. In addition, the edge/corner localization of active orbitals is found for the wider and longer GNPs.

The reaction of pyridinium chlorochromate with furan to give enedione derivatives cannot be performed by using commercial PCC. Homemade and commercial PCC had different color and showed some differences in the XRD spectrum. XPS showed the presence of relevant amount of Cr(III) in the homemade reagent. DFT calculations showed that Cr(III) impurities in the reagent can catalyze the reaction with furan derivatives, if oxygen atom in the Cr(III) derivative attacks the furan ring, while it is reoxidized by PCC, through a migration of a chlorine atom.

Molecular structures, in chloroform and DMSO solution, of the monounsaturated free fatty acids (FFAs) caproleic acid (dec-9-enoic acid) and oleic acid (octadec-9-enoic acid) and the ω-3 FFAs α-linolenic acid (9Z,12Z,15Z)-octadeca-9,12,15-trienoic acid ALA), eicosapentanoic acid (5Z,8Z,11Z,14Z,17Z)-icosa-5,8,11,14,17-pentaenoic acid) and docosahexaenoic acid (4Z,7Z,10Z,13Z,16Z,19Z)-docosa-4,7,10,13,16,19-hexaenoic acid), are reported with the combined use of NMR and DFT calculations. Variable temperature and concentration chemical shifts of the COOH protons and transient 1D NOE experiments, in CDCl3, demonstrate the major contribution of low molecular weight aggregates of dimerized fatty acids, through intermolecular hydrogen bond interactions of the carboxylic groups, with parallel and antiparallel interdigitated structures, even at the low concentration of 20 mM. For the dimeric DHA, a structural model of an intermolecular hydrogen bond through carboxylic groups and an intermolecular hydrogen bond between the carboxylic group of one molecule and the ω-3 double bond of a second molecule, is shown to play a role. In DMSO-d6 solution the centro-symmetric hydrogen bond interactions are broken and the carboxylic groups form strong intermolecular hydrogen bond interactions with a discrete solvation molecule of DMSO. These solvation species form parallel and antiparallel interdigitated structures of low molecular weight. DFT structural models in CHCl3 and DMSO, in agreement with the NMR data, are compared with the structures in the liquid state

In recent years, two-dimensional (2D) materials have attracted significant attention due to their distinctive properties, including exceptional mechanical flexibility and tunable electronic properties. Via the first-principles calculation, we investigate the effect of strain on the electronic properties of monolayer SnP2S6 and GeP2S6. We find that monolayer SnP2S6 is an indirect band gap semiconductor, while monolayer GeP2S6 is a direct band gap semiconductor. Notably, under uniform biaxial strains, SnP2S6 undergoes an indirect-to-direct band gap transition at 4.0% biaxial compressive strains, while GeP2S6 exhibits a direct-to-indirect transition at 2.0% biaxial tensile strain. The changes of the conduction band edge can be attributed to the high-symmetry point Γ being more sensitive to strain than K. Thus, the relocation of the conduction-band and valence-band edges in monolayer SnP2S6 and GeP2S6 induces a direct-to-indirect and indirect-to-direct band-gap transition respectively. Consequently, the strain is an effective band engineering scheme which is crucial for the design and development of next-generation nanoelectronic and optoelectronic devices.

Luminophores featuring thermally activated delayed fluorescence (TADF luminophores) are the workhorse of the third- and fourth-generation OLEDs. While these compounds had usually been used as dopants embedded in the host, non-doped TADF OLEDs have recently shown significant progress as well reaching the performance comparable to the host-dopant ones. For efficient operation of the non-doped OLEDs, charge transport in neat films and single crystals of TADF luminophores is important; however, this issue was nearly unexplored theoretically. In the current study, we calculated charge mobilities in four TADF single crystals, which have different molecular packing motifs. Specifically, in one of them both donor and acceptor moieties form uniform π-stacks, while in the others donors (acceptors) show alternating lateral shifts along the stacks; the difference in molecular packing results in the difference of transfer integral between the molecules. Reorganization energies differ as well up to four times for the studied crystals. As a result, charge mobilities vary from 0.001 to ~0.3 cm2/(V∙s), the largest being predicted for the crystal of the luminophore consisting of rigid donor and acceptor. We anticipate that the results obtained can be useful for the design of TADF luminophores for non-doped OLEDs, OLETs and other organic light-emitting devices.

This study reports a computational investigation on the antioxidant activity of five plant food benzoic acid derivatives, namely gallic acid (GA), para-hydroxybenzoic acid (PHBA), protocatechuic acid (PCA), syringic acid (SA), and vanillic acid (VA). Based on computed thermodynamics parameters, a detailed comparative debate is developed concerning their free radical scavenging activity in the gas phase and polar solutions (in water and methanol solvents). This discussion goes on to elucidate both the most preferred mechanism and the order of antioxidant activity for these molecules in each environment. Paradoxically, calculations using the harmonic oscillator model of aromaticity (HOMA) suggest that H abstraction radicals gain in stability as the central benzene ring loses in structural aromaticity. Finally, spin densities and fukui function f⁰ seem to be good indicators of the local reactivity of these compounds towards free radicals.

In two-dimensional materials research, oxidation is usually considered as a common source for the degradation of electronic and optoelectronic devices or even device failure. However, in some cases a controlled oxidation can open the possibility to widely tune the band structure of 2D materials. In particular, we demonstrate the controlled oxidation of titanium trisulfide (TiS₃), a layered semiconductor that attracted much attention recently thanks to its quasi-1D electronic and optoelectronic properties and its direct bandgap of 1.1 eV. Heating TiS₃ in air above 300 °C gradually converts it into TiO₂, a semiconductor with a wide bandgap of 3.2 eV with applications in photo-electrochemistry and catalysis. In this work, we investigate the controlled thermal oxidation of individual TiS₃ nanoribbons and its influence on the optoelectronic properties of TiS₃-based photodetectors. We observe a step-wise change in the cut-off wavelength from its pristine value ~1000 nm to 450 nm after subjecting the TiS₃ devices to subsequent thermal treatment cycles. Ab-initio and many-body calculations confirm an increase of the bandgap of titanium oxysulfide (TiO_2-xS_x) when increasing the amount of oxygen and reducing the amount of sulfur.

To realize high response and selectivity gas sensor in detecting dissolved gases in transformer oil, in this study, the adsorption of four kinds of gases (H2, CO, C2H2 and CH4) on Pd-graphyne as well as the gas sensing properties evaluation were investigated. The energetically favorable structure of Pd doped γ-Graphyne was first studied, including the comparison of different adsorption sites and discussion of electronic properties. Then, the adsorption of these four molecules on Pd-graphyne was explored. The adsorption structure, adsorption energy, electron transfer and electron distribution, the band structure and density of states were calculated and analyzed. The results show that the Pd atom prefers to be adsorbed on the middle of three C≡C bonds and the band gap is smaller. The CO adsorption exhibits the largest adsorption energy and electron transfer and brings obvious change to the structure and electron properties to Pd-graphyne. Because of the conductance decrease after adsorption CO and acceptable recovery time at high temperature, the Pd-graphyne can be promising gas sensing materials to detect CO with high selectivity. This work offers theoretical support for the design of nanomaterials based gas sensor using novel structure for industrial application.

A series of Cu(II)-thiocyanato complexes derived from sterically hindered N-donors diamines were synthesized and characterized: catena-[Cu(Me₃en)(μ-NCS)(NCS)] (1), catena-[Cu(NEt₂Meen)(μ-NCS)(NCS)] (2), catena-[Cu(N,N,2,2-Me₄pn)(μ-NCS)(NCS)] (3), the dimeric: [Cu₂(N,N′-isp₂en)₂(μ-NCS)₂(NCS)₂] (4) and the monomeric complex [Cu(N,N′-t-Bu₂en)(NCS)₂] (5), where Me₃en = N,N,N′-Trimethylethylenediamine, NEt₂Meen = N,N-diethyl-N′-methylethylenediamine, N,N,2,2-Me₄pn = N,N,2,2-tetramethylpropylenediamine, N,N′-isp₂en = N,N′-diisopropylethylenediamine and N,N′-t-Bu₂en = N,N′-di(tert-butyl)ethylenediamine. The complexes were characterized by elemental microanalyse, IR and UV-Vis spectroscopy and single crystal X-ray crystallography. Density Functional Theory was used to evaluate the role of steric effects in compounds 4 and 5 and how this may affect the adaption of a specific geometry, NCS-bonding mode and the dimensionality of the resulting complex.

Silicates are among the most abundant and important inorganic materials, not only in the Earth’s crust but also in the interstellar medium in the form of micro-/nano-particles or embedded in the matrices of comets, meteorites and other asteroidal bodies. Although the crystalline phases of silicates are indeed present in Nature, amorphous forms are also highly abundant. Here we report a theoretical investigation of the structural, dielectric and vibrational properties of the amorphous bulk for forsterite (Mg₂SiO₄) as a silicate test case by a combined approach of classical molecular dynamics (MD) simulations for structure evolution, and periodic quantum mechanical DFT calculations for electronic structure analysis. Using classical MD based on an empirical partial charge rigid ionic model within a melt-quenching scheme at different temperatures performed with the GULP 4.0 code amorphous bulk structures for Mg₂SiO₄ were generated using as initial guess the crystalline phase. This has been done for bulks with three different unit cell sizes adopting a super-cell approach; i.e., 1×1×2, 2×1×2 and 2×2×2. The radial distribution functions indicated a good degree of amorphisation of the structures. Periodic B3LYP-geometry optimizations performed with the CRYSTAL14 code on the generated amorphous systems were used to analyze their structure, to calculate their high frequency dielectric constants (ε_∞), and to simulate the IR, Raman and reflectance spectra, which were compared with the experimental and theoretical crystalline Mg₂SiO₄. The most significant changes of the physico-chemical properties of the amorphous systems compared to the crystalline ones are presented and discussed (e.g., larger deviations in the bond distances and angles, broadening of the IR bands, etc.), which are consistent with their disordered nature. It is also shown that by increasing the unit cell size the bulk structures present larger degree of amorphisation.

It is always a difficult task to assign the peaks recorded from vibrational spectrum. Herein we explored a new pathway of density functional theory (DFT) simulation to present three kinds of spectra of ice XIV and can be referenced as inelastic neutron scattering (INS), IR, and Raman experimental spectrum. The INS spectrum is proportional to phonon density of states (PDOS) while the photon scattering signals reflect the normal vibration frequencies near the Brillouin zone (BZ) center. Based on good agreements with experimental data, we identified the relative frequency and made scientific assignments by normal vibration modes analysis. The debating two hydrogen bond (H-bond) peaks among ice phases from INS have been discussed and the dynamic process of H-bond vibrations were found to be classified into two basic modes. we deduce that two H-bond modes are a general rule among ice family and more works are ongoing to investigate this subject.

The laser host materials undergo relatively small changes in their intrinsic properties due to various sources during an experiment. These sources are often related to temperature change or applied stress, which may cause change in optical properties of the material under study. Consequently, the crystal experiences an optical anisotropy, which may affect the final outcome of the experiments. One way to reduce probable noises is to predict the change in optical properties with respect to load. To predict the changing pattern of the refractive index in a crystal, one needs to know both the elastic and photoelastic constants of the material. In this study, we utilized density functional perturbation theory (DFPT) to extract the photoelastic tensor of Y$_2$SiO$_5$ and Eu-doped Y$_2$SiO$_5$ crystals. Using the photoelastic and elastic constants calculated, a Finite Element (FE) model was developed, which allowed us to apply load and then post-process the results. This methodology enabled us to observe the variation in refractive index ($n$), and consequently, the shift in the resonance frequency of the cavity. The results obtained were in agreement with experimental measurements, falling within a 3\% discrepancy across a temperature range spanning from cryogenic to room temperature. This correlation suggests the feasibility of using the current workflow as a predictive tool for evaluating variations in refractive indices over a specific interval.

Field electron emission, or electron tunneling through a potential barrier under the influence of a strong electrostatic field, is of broad interest to the accelerator physics community. For example, it is the source of undesirable dark currents in resonant cavities, providing a limit to high-field operation. The classical approach to field electron emission is the Fowler-Nordheim (FN) framework, which incorporates a simplified surface potential and various assumptions. Here we build a more realistic model using the potential and charge densities derived from a density-functional theory (DFT) calculation. We examine the correction factors associated with each model assumption. Compared to the FN framework, our results can be extended up to 80 GV/m, a limit that has been reached in laser-induced strong field emission scenarios.

Using first-principles molecular dynamics (FPMD), we performed numerical simulations at 300 K to explore the interaction of a 2D MoS2 surface and a platinum atom, calculating the optical properties of the resulting material. The pristine MoS2 is a semiconductor with a gap of around 1.8 eV. The Pt atom is chemisorbed by the surface with an adsorption energy of −1.718 eV. With the adsorption of the Pt atom, the material remains a semiconductor, and its energy band gap reduces to 1.04 eV. But changes in the material's energy band structure imply substantial changes in its optical properties. The energy band structure of the 2D MoS2 with a sulfur vacancy VS shows that the material becomes a conductor, and there are significant changes in its optical properties. We also found that the Pt atom chemisorbs in a sulfur vacancy of the material, with an adsorption energy of −4.1164 eV. After the adsorption of Pt atoms in the sulfur vacancy, the material becomes a semiconductor with a band gap of 1.06 eV, and the changes in the optical absorption and reflectivity are significant.

Carbazole is one of the typical heterocyclic aromatic compounds (NSO-HETs) observed in pol-luted urban atmosphere, which has become a serious environmental concern. The most im-portant atmospheric loss process of carbazole is the reaction with OH radical. The present work investigated the mechanism of OH-initiated atmospheric oxidation degradation of carbazole by using density functional theory (DFT) calculations at the M06-2X/6-311++G(3df,2p)//M06-2X/6-311+G(d,p) level. The rate constants were determined by the Rice-Ramsperger-Kassel-Marcus (RRKM) theory. The lifetime of carbazole determined by OH was compared with other typical NSO-HETs. The theoretical results show that the degradation of carbazole initiated by OH radical includes four types of reactions: OH additions to “bend” C atoms, OH additions to “benzene ring” C atoms, H abstractions from C-H bonds and the H ab-straction from N-H bond. The OH addition to C1 atom and the H abstraction from N-H bond are energetically favorable. The main oxidation products are hydroxycarbazole, dialdehyde, carba-zolequinone, carbazole-ol, hydroxy-carbazole-one and hydroperoxyl-carbazole-one. The calcu-lated overall rate constant of carbazole oxidation by OH radical is 6.52 × 10−12 cm3 molecule−1 s−1 and the atmospheric lifetime is 43.92 h under the condition of 298 K and 1 atm. The lifetime of carbazole determined by OH radical is similar with that of dibenzothiophene oxidation but longer than those of pyrrole, indole, dibenzofuran and fluorene. This work provides a better understanding of the reactivity of carbazole in the atmospheric environment, the formation of secondary organic aerosols, and the chemical degradation and removal of carbazole in the at-mospheric environment.

The electronic structural evolution of LLM-105 crystal and the (101) plane of LLM-105 crystal under different pressures is investigated by the density functional theory (DFT) calculations and the surface properties of seven low-Miller-index planes of LLM-105 crystal were investigated in this study. The result demonstrates that the surface energy of (101) plane of LLM-105 is much smaller when compared with other low-Miller-index planes of LLM-105.In order to further investigate the stability of crystal structure and (101) plane of LLM-105 under different pressures, a series of pressures ranged from 0 GPa to 55 GPa were applied during the DFT calculation, and the result shows that the electronic structures of LLM-105 crystal and the (101) plane changed with the increase of external pressure and the evolution process of (101) plane is different from that of LLM-105 crystal structure.

The [3+2] cycloaddition (32CA) reactions of strongly nucleophilic norbornadiene (NBD) with simplest diazoalkane (DAA) and three DAAs of increased electrophilicity have been studied within the Molecular Electron Density Theory (MEDT) at the MPWB1K/6-311G(d,p) computational level. These pmr-type 32CA reactions follow an asynchronous one-step mechanism with activation enthalpies ranging from 17.7 to 27.9 kcal·mol-1 in acetonitrile. The high exergonic character of these reactions makes them irreversible. The presence of electron-withdrawing (EW) substituents in the DAA increases the activation enthalpies, in complete agreement with the experimental slowing-down of the reactions, but contrary to the Conceptual DFT prediction. Despite the nucleophilic and electrophilic character of the reagents, the global electron density transfer at the TSs indicates rather non-polar 32CA reactions. The present MEDT study allows establishing that the depopulation of the NNC core in this series of DAAs with the increase of the EW character of the substituents present at the carbon center is responsible for the experimentally found deceleration.

In recent years extensive studies have been continuously undertaken on the design of bioactive and biomimetic dental implant surfaces due to the need for improvement of the implant-bone interface properties. In this paper, the titanium dental implant surface was modified by a bioactive vitamin D3 coating prepared by self-assembly process. Surface characterization of the modified implant was performed by field emission scanning electron microscopy (FE-SEM), attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), and contact angle measurements (CA). Implant’s electrochemical stability during exposure to an artificial saliva solution was monitored in situ by electrochemical impedance spectroscopy (EIS). Experimental results obtained were corroborated by means of quantum chemical calculations at the density functional theory level (DFT). The formation mechanism of the coating onto the titanium implant surface was proposed. During a prolonged immersion period, the bioactive vitamin D3 coating effectively prevented the underlying titanium from corrosive attack (polarization resistance in order of 10⁷ Ω cm²) with ~95% protection effectiveness.

A typical vibrational spectrum in the ice phase has four separate bands: translation, libration, bending and stretching. Ice X, the final ice phase under high pressure, shows an exotic vibrational spectrum. Theoretically, an ideal crystal of ice X only has one peak at 998 cm-1 for Raman scattering and two peaks at 450 cm-1 and 1507 cm-1 for infrared absorption in this work. These three characteristic peaks are indicators of the phase transition between ice VII/VIII and ice X. Despite much experimental and theoretical work on ice X, only this study has clearly indicated these characteristic peaks in the region of the IR band. The phonon density of states shows quite different features than ice VIII, which could be verified by inelastic neutron scattering in the future. The dynamic processes of 15 vibrational normal modes are discussed and the typical hydrogen bonds are missing.

As the smallest member of the fullerene family, C20 is yet to be discovered in planetary nebulae. In this work, we present a quantum chemical study via density functional theory (DFT) on the ionization tolerance of this molecule in the space environment. Considering that the ionization and excitation phenomena play key roles in alerting the lifetime of a molecule, we examined both ground and excited electronic states potential energy surfaces (PES) of C20 and its cations C20q+. Our theoretical results indicate that the C20 cage tolerates a positive charge as high as 13+ via characterizing local minimum geometries on both mentioned electronic states. We also explored theoretically and systematically, scenarios in which the electronic structure of neutral C20 is excited to very high spin multiplicity (beyond triplet state) and local minimum molecular geometries with cage structure are well characterized. We anticipate that such structural resistance to excitation and ionization deliver a prolonged lifetime necessary for the spectroscopic detection of this interesting molecule and its cations in space and potentially in planetary nebulea (PN).

Density functional theory (DFT) calculations of hydrogen adsorption on titanium nitride had previously shown that hydrogen may adsorb on both titanium and nitrogen sites with a moderate adsorption energy. Further, the diffusion barrier was also found to be low. These findings may qualify TiN, a versatile multifunctional material with electronic conductivity, as electrode material for the hydrogen evolution reaction (HER). This was the main impetus of this work which aims to experimentally and theoretically investigate the electrocatalytic properties of TiN-layers that were processed on Ti substrate using reactive ion sputtering. The properties are discussed focusing on the role of oxygen defects introduced during the sputtering process on the HER. Based on DFT calculations, it is shown that these oxygen defects alter the electronic environment of the Ti atoms which entails a low hydrogen adsorption energy in the range of -0.1 eV; this leads to HER performances that match those of Pt-NPs in acidic media. When a few nanometr thick layer of Pd-NPs is sputtered on-top of the TiN-layer, the performance is drastically reduced. This is interpreted in terms of oxygen defects being scavenged by the Pd-NPs near the surface which is thought to reduce the hydrogen adsorption sites.

Due to increasing concerns about global warming and energy crisis, intensive efforts have been made to explore renewable and clean energy sources. Single-atom metals and two-dimensional (2D) nanomaterials have attracted extensive attention in the fields of energy and environment because of their unique electronic structures and excellent properties. In this review, we sum-marize the state-of-art progress on the single-atom metal supported at 2D MoS2 (single-atom metal/2D MoS2) for electrochemical CO2 reduction and water splitting. First, we introduce the advantages of single-atom metal/2D MoS2 catalysts in the fields of electrocatalytic CO2 reduction and water splitting, followed by the strategies for improving electrocatalytic performances of single-atom metal/2D MoS2 hybrid nanomaterials and the typical preparation methods. Further, we discuss the important applications of the nanocomposites in electrocatalytic CO2 reduction and water splitting via some typical examples, particularly focusing on their synthesis routes, modification approaches, and physiochemical mechanisms for improving their electrocatalytic performances. Finally, our perspectives on the key challenges and future directions of exploring high-performance metal single-atom catalysts are presented based on recent achievements in the development of single-atom metal/2D MoS2 hybrid nanomaterials.

Understanding the structure and properties of MgCl2/TiCl4/ID nanoclusters is a key to uncover the origin of Ziegler-Natta catalysis. In this work MgCl2/TiCl4 nanoplatelets derived by machine learning and DFT calculations have been used to model the interaction with ethyl-benzoate EB (as internal donor) with available exposed sites of binary TixCly/MgCl2 systems. The influence of vicinal Ti2Cl8 and coadsorbed TiCl4 on energetic, structural and spectroscopic behaviour of EB has been considered. The adsorption of homogeneous-like TiCl4EB and TiCl4(EB)2 at the various surface sites have been also simulated. Calculations have been carried out by employing B3LYP-D2 and M06 functionals. The adducts have been characterized by computing IR and Raman spectra that have been found to provide specific fingerprints useful to identify surface species; IR spectra have been successfully compared to available experimental data.

In this work, we investigate by ab initio calculations and optical experiments the sensitiv- ity of graphene quantum dots in their use as devices to measure the presence, and concentration, of heavy metals in water. We demonstrate that the quenching or enhancement in the optical response (absorption, emission) depends on the metallic ion considered. In particular, two test cases of opposite behaviour are considered: Cd 2+ , where we observe an increase in the optical response for increasing concentration, and Pb 2 whose emission spectra are quenched along the concentration rise. We envisage that quantum dots of graphene may be routinely used as cheap detectors to measure the degree of poisoning ions in water

Knowledge about the formation energies of compounds is essential to derive phase diagrams of multi-component phases with respect to elemental reservoirs. The determination of formation energies using common (semi-)local exchange-correlation approximations of density functional theory (DFT) exhibits well-known systematic errors if applied to oxide compounds containing transition metal elements. In this work, we generalize, reevaluate and discuss a set of approaches proposed and widely applied in the literature to correct for errors arising from the over-binding of the O2 molecule and from correlation effects of electrons in localized transition-metal orbitals. The DFT+U method is exemplarily applied to iron oxide compounds, and a procedure is presented to obtain U values, which lead to formation energies and electronic band gaps comparable to experimental values. Using such corrected formation energies, we derive the phase diagrams for LaFeO3, Li5FeO4 and NaFeO2, which are promising materials for energy conversion and storage devices. A scheme is presented to transform the variables of the phase diagrams from the chemical potentials of elemental phases to those of precursor compounds of a solid-state reaction, which represents the experimental synthesis process more appropriately. The discussed workflow of methods can directly be applied to other transition metal oxides.

Novel collector lead(II)-benzohydroxamic acid (Pb(II)-BHA) complexes in aqueous solution were characterized by using experimental approaches, including Ultraviolet-visible (UV-Vis) spectroscopy and electrospray ionization–mass spectrometry (ESI-MS), as well as first-principle density functional theory (DFT) calculations with consideration for solvation effects. The Job plot delineated that a single coordinated Pb(BHA)⁺ should be formed first, and the higher coordination number complexes can be formed subsequently. Moreover, the Pb(II)-BHA species can aggregate with each other to form complicated structures, such as Pb(BHA)₂ or highly complicated complexes. ESI-MS results validated the existence of Pb-(BHA)_n=1,2 under different solution pH values. Further, the first-principles calculations suggested that Pb(BHA)⁺ should be the most stable structure, and the Pb atom in Pb(BHA)⁺ will act as an active site to attack nucleophiles. These findings are meaningful to further illustrate the adsorption mechanism of Pb(II)-BHA complexes in mineral processing.

In this work, a new hybrid compound3,4-diaminopyridinium perchlorate with the formula (C5H8N3)ClO4abbreviated 3,4-DAPP was synthesized in aqueous solution at room temperature by the slow evaporation method. It crystallizes in the monoclinic system,with a non-centrosymmetric space group P21with the following parameters: a=5.1261 (9), b=9.3003 (17),c=8.6659 (16) Å and β=102.595 (7) °. However, the supramolecular crystal structure was built from perchlorate anions (ClO4)- and organic diaminopyridinum cations (C5H8N3)+connected with hydrogen bonds to form a three-dimensional network. Fourier transform infrared (FTIR) and Raman spectra indicate that the vibrational modes correspond to both inorganic and organic entities. According to Hirschfeld’s analysis, the crystal packing is mainly stabilizedby the presence of hydrogen bonds O⋯H (50%), as well as the crystal void analysis indicates the mechanical stability of the structure. Furthermore, the thermal behavior studied by thermogravimetric (TGA-DTA) and differential scanning calorimetry (DSC) appears to have good stability up to 280°C. Finally, the optical properties were investigated by UV-Vis absorption and photoluminescence spectroscopy along with density-functional theory DFT calculations, whichexhibit emission property, and a band gap energy of 3.9 eV.Additionally, biological activity tests revealed that 3,4-DAPP exhibited moderate antibacterial activity, particularly against Bacillus cereus, though it was less effective than 3,4-diaminopyridine (3,4-DAP) against several other bacteria, indicating that the perchlorate group in 3,4-DAPP may reduce its antimicrobial efficacy.

The reaction mechanisms of C-S borylation of aryl sulfides catalyzed by the 1,4-benzoquinone (BQ), were investigated by employing M06-2X-D3/ma-def2SVP method and basis set. In this study, the SMD model was taken to simulate the solvent effect of 1,4-dioxane. Also, TD-DFT calculations of BQ and methyl(p-tolyl)sulfane were performed in SMD solvent model. The computational results indicated that BQ and methyl(p-tolyl)sulfane, serving as a photo-catalyst, would be excited under blue LED of 450 nm, aligning well with experimental observations. Additionally, the role of 3O2 was investigated, revealing that it could be activated to 1O2 from the released energy of 1[BQ+methyl(p-tolyl)sulfane]* or 3[BQ+ methyl(p-tolyl)sulfane]*→BQ+ methyl(p-tolyl)sulfane process. Then 1O2, bis(pinacolato)diboron, and methyl(p-tolyl)sulfane would through a series of reactions to yield the final product P. The Gibbs free energy surface show that path a2-2 is optimal and this path has less steps and lower energy barrier. The electron spin density isosurface graphs were employed to analyze structures and elucidate the single electron distribution. These computational results offer valuable insights into the studied interactions and related processes and shed light on the mechanisms governing C–S borylation from aryl sulfides and b2pin2 catalyzed by BQ and methyl(p-tolyl)sulfane.

With the aim to produce new heterocycle molecules, the previously reported 2-(aminomethyl)-2-(4-chlorophenyl)-2,3-dihydroquinazolin-4(1H)-one was converted efficiently by reacting with N,N’-dithiocarbonyldiimidazole (DTCI), to produce the substituted imidazolidine-2-thione moiety inserted in a three fused ring scaffold of the title compound. The molecular composition was confirmed by a high-resolution MS experiment, and its structure was elucidated by 1H, 13CNMR, and IR analyses. The thioacetamide form of the product was supported by density functional theory (DFT)-NMR analysis where 13C chemical shifts of thioacetamide form and of its iminothiol tautomer were calculated in chloroform at the BP86 /Jgauss-TZP2 level of theory. The very good linear correlation between 13C chemical shifts by experiment and by calculation for the NHC=S form confirmed the structure.

Stellatolides are natural compounds that have shown promising biological activities, including antitumor, antimicrobial, and anti-inflammatory properties, making them potential candidates for drug development. Chemical Reactivity Theory (CRT) is a branch of chemistry that explains and predicts the behavior of chemical reactions based on the electronic structure of molecules. Conceptual Density Functional Theory (CDFT) and Computational Peptidology (CP) are computational approaches used to study the behavior of atoms, molecules, and peptides. In this study, we present the results of our investigation of the chemical reactivity and ADMET properties of Stellatolides A-H using a novel computational approach called Conceptual DFT-based Computational Peptidology (CDFT-CP). Our study uses CDFT and CP to predict the reactivity and stability of molecules and to understand the behavior of peptides at the molecular level. We also predict the ADMET properties of the Stellatolides A-H to provide insight into their effectiveness, potential side effects, and optimal dosage and route of administration. This study sheds light on the potential of Stellatolides A-H as promising candidates for drug development and highlights the potential of CDFT-CP for the study of other natural compounds and peptides.

[Co(AMPY)(DAPY)Cl2(H2O)].H2O (1) [Cu(AMPY)(DAPY)Cl2(H2O)].H2O (2) [Zn(AMPY)(DAPY)Cl2(H2O)] (3) were prepared from the ligands; AMPY = 2-amino-4-methylpyrimidine (L1), DAPY = 2,3-diaminopyridine (L2) and CoCl2.6H2O, CuCl2.2H2O and ZnCl2 in water/ethanol solutions and the three products characterized by elemental analysis, ultraviolet-visible spectroscopy (UV–Vis), Fourier-transform infrared spectroscopy (FT-IR), magnetic susceptibility, molar conductivity methods, and TGA analysis. The X-ray powder diffraction of the Co(II), Cu(II), and Zn(II) compounds showed that the geometry of monoclinic and SEM analysis revealed their morphology with a smooth surface. Molecular modeling was performed for all compounds using the density functional method DFT/B3LYP to study the structures and the frontier molecular orbitals (HOMO and LUMO). We have used Gaussian09 software for the calculations. In this study, different complexes were tested against Gram negative and Gram positive bacterial species to give insight into their broad-spectrum effects. The used pathogenic strains were two Gram positive species "Staphylococcus aureus and Micrococcus luteus" and two Gram negative species "Salmonella thyphimurium and Escherichia coli. The antifungal activity was evaluated against a pathogenic reference strain of the yeast Candida albicans. The antimicrobial and antioxidant assay results demonstrate that the tested compounds are effective against Gram positive and negative bacteria. Additionally, the compounds have an antifungal effect against Candida albicans with a maximum inhibitory zone of 2.5cm. The results demonstrated high antioxidant potential for the Zn(II) complex with a DPPH scavenging of 91.5%, however, the Cu(II) complex was low (16.5%). The data of docking with tyrosyl-tRNA synthetase presented that all compounds fit very well in the catalytic pockets of the proteins of the receptor.

Using density functional theory (DFT) and the information-theoretic approach (ITA) quantities to appreciate the energetics and properties of biopolymers is still an unaccomplished and ongoing task. To this end, we studied the building blocks of nucleic acid base pairs and small peptides. For base pairs, we have dissected the relative importance of energetic components by using two energy partition schemes in DFT. Our results convincingly show that the exchange-correlation effect predominantly governs the molecular stability of base pairs while the electrostatic potential plays a minor but indispensable role, and the steric effect is trivial. Furthermore, we have revealed that simple density-based ITA functions are in good relationships with molecular polarizabilities for a series of 30 hydrogen-bonded base pairs and all 20 natural α-amino acids, 400 dipeptides, and 8000 tripeptides. Based on these lines, one can easily predict the molecular polarizabilities of larger peptides, even proteins as long as the total molecular wavefunction is available, rather than solving the computationally demanding coupled-perturbed Hartree-Fock (CPHF) equation or its DFT counterpart coupled-perturbed Kohn-Sham (CPKS) equation.

According to our previous investigation the total methanol extract from Graptopetalum paraguayense E. Walther demonstrates a significant inhibitory effect on HSV-1. To clarify what causes this inhibitory activity on HSV-1, a metabolic profile of the plant was performed. Three main fractions: non-polar substances, polar metabolites and phenolic compounds were obtained and GC-MS analysis was carried out. Since it is well known that phenolic compounds show a significant anti-herpes effect and that viral DNA polymerase (DNApol) appears to play a key role in HSV virus replication, we present a docking and quantum-chemical analysis of the binding of these compounds to viral DNApol amino acids. Fourteen different phenolic acids found by GS/MS analyses, were used in molecular docking simulations. According to the interaction energies of all fourteen ligands in the DNApol pockets based on docking results, DFT calculations were performed on the five optimally interacting with the receptor acids. It was found that hydroxybenzoic acids from phenolic fraction of Graptopetalum paraguayense E. Walther show a good binding affinity to the amino acids from the active site of the HSV DNApol, but significantly lower than that of acyclovir. The mode of action on virus replication of acyclovir (by DNApol) is different from that of the plant phenolic acids one, probably.

Azobenzene-containing molecules may associate with each other in systems such as self-assembled monolayers or micelles. The interaction between azobenzene units leads to a formation of exciton states in these molecular assemblies. Apart from local excitations of monomers, the electronic transitions to the exciton states may involve charge transfer excitations. Here, we perform quantum chemical calculations and apply transition density matrix analysis to quantify local and charge transfer contributions to the lowest electronic transitions in azobenzene dimers of various arrangements. We find that the transitions to the lowest exciton states of the considered dimers are dominated by local excitations, but charge transfer contributions become sizable for some of the lowest ππ* electronic transitions in stacked and slip-stacked dimers at short intermolecular distances. In addition, we assess different ways to partition the transition density matrix between fragments. In particular, we find that the inclusion of the atomic orbital overlap has a pronounced effect on quantifying charge transfer contributions if a large basis set is used.