Monte Carlo Simulation of Crystal-Liquid Phase Coexistence

Abstract

When a crystal nucleus is surrounded by coexisting fluid in a finite volume in thermal equilibrium, the thermodynamic properties of the fluid (density, pressure, chemical potential) are uniquely related to the surface excess free energy of the nucleus. Using a model for weakly attractive soft colloidal particles, it is shown that this surface excess free energy can be determined accurately from Monte Carlo simulations over a wide range of nucleus volumes, and the resulting nucleation barriers are completely independent from the size of the total volume of the system. A necessary ingredient of the analysis, the pressure at phase coexistence in the thermodynamic limit, is obtained from the interface velocity method. Computing the solid-liquid interface excess free energy via the ensemble switch method, a detailed test of classical nucleation theory is possible (assuming the hypothetical spherical nucleus shape, which is not realized when the crystal nucleus is facetted). Consequences for the interpretation of experiments will be briefly discussed.