Improving the understanding of the melting behaviour of Mo, Ta, and W at extreme pressures

TL;DR

This paper investigates the melting behavior of Mo, Ta, and W at extreme pressures, proposing vacancy formation and a modified Lindemann law to reconcile experimental and theoretical discrepancies, and suggests a new high-pressure phase.

Contribution

It introduces a vacancy-based explanation for melting curves and modifies the Lindemann law with a power series Grueneisen parameter for better fit.

Findings

Vacancy formation explains melting curve discrepancies.

Modified Lindemann law fits all measured melting curves.

Proposes existence of an extra high P-T phase for Mo, Ta, and W.

Abstract

We discus existent conflicts between experimentally measured and theoretically calculated melting curves of Mo, Ta, and W. By assuming that vacancy formation plays a fundamental role in the melting process, an explanation for the measured melting curves is provided. Furthermore, we show that the Lindemann law fits well all the measured melting curves of bcc transition metals if the Grueneisen parameter is written as a power series of the interatomic distance. For completeness, we examine possible reasons for current disagreements between shock-wave and DAC experiments. To solve them, we propose the existence of an extra high P-T phase for Mo, Ta, and W