Pressure Renormalization for Premelting Phenomena

Abstract

We develop the pressure renormalization of a phonon potential for atoms interacting anharmonically, starting from a fully dynamical Hamiltonian description in pseudoharmonic approximation. We derive a generalized equation for the correlation function of atom–atom displacement across a thin film, which under certain conditions reduces to the one previously discussed in the literature. Our theory yields expressions for a series of melting temperatures in terms of the microscopic parameters of a layered system using Lindemann's argument. The global instability temperature is obtained due to the distribution of displacement correlations in the surface region while the local melting transition is recognized as a process of surface premelting which expands into the stable bulk with increasing temperature. The pressure dependencies of instability and premelting temperatures are mainly discussed.