Statistical mechanics study of solid-solid interfaces. (Progress report).

摘要

The goal of the research project was to employ concepts from statistical mechanics to simplify and extend the classical approaches to the atomistic simulation of interfaces. The reason for resorting to statistical mechanics method was to determine the thermodynamic properties of interfaces in a sufficiently accurate and computationally efficient manner in order to predict the systematic trends (with temperature, interface crystallography, etc.) in the interfacial properties of real materials. The original approach adopted was based on statistical-mechanical density-functional methods. In these methods, the free energy of the system is written as a functional of the atomic density, that is expanded in terms of order parameters that vary smoothly across the interface. After devoting several months to this procedure, we came to the conclusion that it would not provide a sufficiently accurate and tractable approach to meeting the goals of the project. The failure of this approach forced us to examine alternatives that still allowed for the calculation of interfacial thermodynamic properties but that were more accurate and sufficiently computationally tractable that would allow us to truly investigate the systematics of interfacial properties and structure. The approach that was adopted was to write down an approximate free energy functional (in terms of interatomic potentials and atomic coordinates) that could be minimized with respect to atomic positions to obtain finite temperature equilibrium structure and thermodynamics.