Pressure effects of the thortveitite structure of cadmium pyrovanadate Cd2V2O7

Abstract

We report a computational study of cadmium pyrovanadate Cd₂V₂O₇ under ambient and high-pressure conditions using density functional theory. At ambient conditions, the studied pyrovanadate crystalizes in a monoclinic symmetry described by space group C2/m but a triclinic phase described by space group P $\bar{1}$ and a cubic phase described by space group Fd $\bar{3}$ m become stable under high pressure. The optimized structures are consistent with the previous theoretical and experimental studies. We found that the high pressure phases are mechanically stable although the coordination polyhedra of both the Cd and V cations is largely modified. The ambient phase is more compressible than the high-pressure phases. The malleability is also confirmed in all the studied phases. The band gap energies of 2.46 eV, 2.62 eV and 1.50 eV are determined for the studied phases of β-, γ- and τ-Cd₂V₂O₇, respectively. The optical band gap energies, calculated by the Wood-Tauc plot, estimated from the optical absorption spectra are almost similar to the energy gap obtained from their energy dispersion.