Pressure-induced structural phase transition of vanadium: A revisit from the perspective of ensemble theory

TL;DR

This paper revisits the pressure-induced phase transition of vanadium using ensemble theory, successfully calculating the partition function under high pressure and explaining recent experimental observations with theoretical insights.

Contribution

It develops a novel approach to compute the partition function of vanadium under high pressure, providing a theoretical framework that aligns well with experimental data.

Findings

Partition function of vanadium solved up to 320 GPa

Derived equation of state matches experimental measurements

Explains recent phase transition sequences and angles

Abstract

For realistic crystals, the free energy strictly formulated in ensemble theory can hardly be obtained because of the difficulty in solving the high-dimension integral of the partition function, the dilemma of which makes it even a doubt if the rigorous ensemble theory is applicable to phase transitions of condensed matters. In the present work, the partition function of crystal vanadium under compression up to $320$ GPa at room temperature is solved by an approach developed very recently, and the derived equation of state is in a good agreement with all the experimental measurements, especially the latest one covering the widest pressure range up to $300$ GPa. Furthermore, the derived Gibbs free energy proves the very argument to understand most of the experiments reported in the past decade on the pressure-induced phase transition, and, especially, a novel phase transition sequence concerning three different phases observed very recently and the measured angles of two phases agree with our theoretical results excellently.