High-pressure properties of thallium orthovanadate from density-functional theory calculations

Abstract

Thallium vanadate is the missing piece to fully understand the behavior of orthovanadates under high-pressure conditions. Here we report a computational study of TlVO4 under high pressure. Its properties and stability have been studied using the density-functional theory. We have found that TlVO4 undergoes at 2.7 GPa a phase transition from the CrVO4-type structure (described by space group Cmcm) to a wolframite-type structure (described by space group P2/c). In contrast to the behavior of isomorphic vanadates, a subsequent amorphization takes place beyond 6 GPa being it driven by dynamic instabilities. In addition to the structural analysis, we present a systematic study of elastic, vibrational, and bonding properties, as well as a characterization of the electronic band structure and electronic density of states. The distinctive behavior of TlVO4 is attributed to the contribution to the bonding of Tl 6s states. The implications of the observed phase transition and amorphization will be discussed.