Mutter, D.; Urban, D.F.; Elsässer, C. Determination of Formation Energies and Phase Diagrams of Transition Metal Oxides with DFT+U. Materials2020, 13, 4303.
Mutter, D.; Urban, D.F.; Elsässer, C. Determination of Formation Energies and Phase Diagrams of Transition Metal Oxides with DFT+U. Materials 2020, 13, 4303.
Mutter, D.; Urban, D.F.; Elsässer, C. Determination of Formation Energies and Phase Diagrams of Transition Metal Oxides with DFT+U. Materials2020, 13, 4303.
Mutter, D.; Urban, D.F.; Elsässer, C. Determination of Formation Energies and Phase Diagrams of Transition Metal Oxides with DFT+U. Materials 2020, 13, 4303.
Abstract
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.
Keywords
transition metal oxides; density functional theory; DFT+U; materials modelling; phase diagrams
Subject
Chemistry and Materials Science, Materials Science and Technology
Copyright:
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
