Melting and critical superheating

TLDR

Melting can occur heterogeneously at surfaces or homogeneously in the bulk, allowing crystals to be superheated above their melting temperature, yet the physical significance of the superheating limit (TLS) remains unclear. The study aims to show that the solid’s total energy at the superheating limit equals that of its liquid at the melting temperature at constant volume. This is demonstrated using molecular dynamics simulations. At high pressure, the superheating limit and melting temperature satisfy kAB = ln(2/3) = TLS/Tm − 1.

Abstract

Two mechanisms of melting are known, heterogeneous, where melting starts at surfaces, and homogeneous, where the liquid nucleates in the bulk crystal. If melting occurs homogeneously, a crystal can be superheated significantly above its melting temperature $({T}_{m})$. At present, the physical meaning of the limit of superheating $({T}_{\mathit{LS}})$ is unknown. We demonstrate, by molecular dynamics simulations, that the total energy of a solid at ${T}_{\mathit{LS}}$ is equal to the total energy of its liquid at ${T}_{m}$ at the same volume. In the high pressure limit ${T}_{\mathit{LS}}$ and ${T}_{m}$ are connected by the constant ${k}_{AB}=\mathit{ln}\phantom{\rule{0.2em}{0ex}}2∕3$ via the relation ${k}_{AB}={T}_{\mathit{LS}}∕{T}_{m}\ensuremath{-}1$.