Melting of superheated crystals initiates on vacancies

TL;DR

This paper proposes that melting in ideal crystals begins at vacancies where migrating atoms cause vacancy annihilation, leading to local melting and providing a quantitative understanding of melting properties.

Contribution

It introduces a vacancy-decomposition model that explains the initiation of melting at vacancies and offers quantitative predictions for melting point, latent heat, and volume change.

Findings

Melting initiates at vacancies due to atom migration.

The model quantifies melting point, latent heat, and volume change.

Vacancy annihilation triggers local disorder leading to melting.

Abstract

In a large variety of ideal crystals we found that when rapidly migrating atoms squash or annihilate a neighbouring vacancy and produce a disordered cluster, the heat of migration stored in the system exceeds the enthalpy increase required for the coordinating atoms of the vacancy to form a liquid phase, i.e. the liquid phase nucleates from vacancies. Furthermore volumetric analysis supports this well. This vacancy-decomposition model provides quantitative information on the melting point, the latent heat and the volume change upon melting and hence clarifies the mechanism of melting.