Melting of superheated crystals initiates on vacancies

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.