Gonzalez-Platas, J.; Rodriguez-Hernandez, P.; Muñoz, A.; Rodríguez-Mendoza, U.R.; Nénert, G.; Errandonea, D. A High-Pressure Investigation of the Synthetic Analogue of Chalcomenite, CuSeO3∙2H2O. Crystals2019, 9, 643.
Gonzalez-Platas, J.; Rodriguez-Hernandez, P.; Muñoz, A.; Rodríguez-Mendoza, U.R.; Nénert, G.; Errandonea, D. A High-Pressure Investigation of the Synthetic Analogue of Chalcomenite, CuSeO3∙2H2O. Crystals 2019, 9, 643.
Synthetic chalcomenite-type cupric selenite CuSeO3∙2H2O has been studied at room temperature under compression up to pressures of 8 GPa by means of single-crystal X-ray diffraction, Raman spectroscopy, and density-functional theory. According to X-ray diffraction, the orthorhombic phase undergoes an isostructural phase transition at 4.0(5) GPa with the thermodynamic character being first-order. This conclusion is supported by Raman spectroscopy studies which have detected the phase transition at 4.5(2) GPa and by the first-principles computing simulations. The structure solution at different pressures has provided information on the change with pressure of unit-cell parameters as well as on the bond and polyhedral compressibility. A Birch-Murnaghan equation of state has been fitted to the unit-cell volume data. We found that chalcomenite is highly compressible with a bulk modulus of 42 – 49 GPa. The possible mechanism driving changes in the crystal structure is discussed, being the behavior of CuSeO3∙2H2O mainly dominated by the large compressibility of the coordination polyhedron of Cu. On top of that, an assignation of Raman modes is proposed based upon density-functional theory and the pressure dependence of Raman modes discussed. Finally, the pressure dependence of phonon frequencies is also reported.
selenite; chalcomenite; crystal structure; x-ray diffraction; raman spectroscopy; high pressure; equation of state; density functional theory
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