Pressure-induced phase transitions and electronic properties Cd2V2O7

TL;DR

This study uses first-principles calculations to explore pressure-induced structural phase transitions and electronic property changes in Cd2V2O7, revealing two phase transitions and a significant band gap reduction under high pressure.

Contribution

It predicts two structural phase transitions and the stabilization of a cubic pyrochlore structure in Cd2V2O7 under high pressure, providing detailed structural and electronic insights.

Findings

Two phase transitions at 0.3 and 10.9 GPa.

A cubic pyrochlore-type structure stabilizes under compression.

Band gap decreases from 4.39 eV to 2.56 eV after second transition.

Abstract

We report a density-functional theory study of the structural and electronic properties of Cd2V2O7 under high-pressure conditions. The calculations have been performed by using first-principle calculations with the CRYSTAL program. The occurrence of two structural phase transitions, at 0.3 and 10.9 GPa, is proposed. The crystal structure of the different high-pressure phases is reported. Interestingly a cubic pyrochlore-type structure is predicted to stabilize under compression. The two phase transitions involve substantial changes in the coordination polyhedra of Cd and V. We have also determined the compressibility and room-temperature equation of state of the three polymorphs of Cd2V2O7. According to our systematic electronic band-structure calculations, at ambient conditions Cd2V2O7 is an indirect wide band-gap material with a band-gap energy of 4.39 eV. In addition, the pressure dependence of the band gap has been determined. In particular, we have found that after the second phase transition the band gap decreases abruptly to a value of 2.56 eV.