Molecular dynamics study of melting of a bcc metal-vanadium I: mechanical melting

TL;DR

This study uses molecular dynamics simulations to investigate the mechanical melting of bcc vanadium, confirming the Born criterion's applicability and establishing a phase diagram relating melting temperature to defect concentration.

Contribution

It demonstrates that the Born criterion applies to bcc metals and provides a phase diagram of melting temperature versus interstitial defect concentration.

Findings

Critical volume for melting is independent of the melting route.

Mechanical melting occurs when the shear modulus vanishes.

Results are consistent with previous findings for fcc metals like copper.

Abstract

We present molecular dynamics simulations of the homogeneous (mechanical) melting transition of a bcc metal, vanadium. We study both the nominally perfect crystal as well as one that includes point defects. According to the Born criterion, a solid cannot be expanded above a critical volume, at which a 'rigidity catastrophe' occurs. This catastrophe is caused by the vanishing of the elastic shear modulus. We found that this critical volume is independent of the route by which it is reached whether by heating the crystal, or by adding interstitials at a constant temperature which expand the lattice. Overall, these results are similar to what was found previously for an fcc metal, copper. The simulations establish a phase diagram of the mechanical melting temperature as a function of the concentration of interstitials. Our results show that the Born model of melting applies to bcc metals in both the nominally perfect state and in the case where point defects are present.