Phonon instability and structural phase transition in Vanadium under high pressure

TL;DR

This study uses first-principles calculations to predict complex pressure-induced structural phase transitions and phonon instabilities in vanadium, revealing unique behavior not observed in neighboring group-VB metals.

Contribution

It provides the first detailed prediction of a multi-stage phase transition sequence in vanadium under high pressure using ab initio methods.

Findings

Vanadium undergoes a BCC to rhombohedral transition at 60 GPa.

Vanadium's BCC phase becomes unstable at around 112 GPa.

No similar transitions are observed in Nb and Ta.

Abstract

Results of the first-principles calculations are presented for the group-VB metals V, Nb and Ta up to couple of megabar pressure. An unique structural phase transition sequence BCC-->(at 60 GPa) rhombohedral (angle=110.5 degree)-->(at ~ 160 GPa)rhombohedral(angle=108.5 degree)--> (at ~ 430 GPa) BCC is predicted in V. We also find that BCC-V becomes mechanically and vibrationally unstable at around 112 GPa pressure. Similar transitions are absent in Nb and Ta.