A comprehensive experimental and first-principles study on magnesium-vanadium oxides

Magnesium-vanadium oxides have attracted significant attention owing to their promising optical and catalytic properties. Here, experimental and first-principles calculations based on density functional theory (DFT) were combined to examine the electronic, optical, lattice dynamical, and thermodynamic properties of the magnesium pyrovanadate (Mg2V2O7) and magnesium orthovanadate (Mg3V2O8). We first prepare high-purity polycrystalline Mg2V2O7 and Mg3V2O8 crystals using the solid-state reaction method. The good agreement between experimental and theoretical results indicate that these two compounds are ideal candidates for photocatalysts or optoelectronic devices. The lattice dynamics are revealed by Raman spectroscopy and phonon dispersion curves. The thermodynamic properties over a wide range of tem-peratures were also obtained. This study not only promotes the functional applications of Mg2V2O7 and Mg3V2O8 compounds but also highlights a guidance for understanding the thermodynamic phase diagram of magnesium-vanadium oxides. (C) 2021 Elsevier B.V. All rights reserved.