Adjusting the melting point of a model system via Gibbs-Duhem integration: Application to a model of aluminum

Abstract

Model interaction potentials for real materials are generally optimized with respect to only those experimental properties that are easily evaluated as mechanical averages [e.g., elastic constants $(\mathrm{at}T=0\mathrm{}\mathrm{K}),$ static lattice energies, and liquid structure]. For such potentials, agreement with experiment for the nonmechanical properties, such as the melting point, is not guaranteed and such values can deviate significantly from experiment. We present a method for reparametrizing any model interaction potential of a real material to adjust its melting temperature to a value that is closer to its experimental melting temperature. This is done without significantly affecting the mechanical properties for which the potential was modeled. This method is an application of Gibbs-Duhem integration [D. Kofke, Mol. Phys. 78, 1331 (1993)]. As a test we apply the method to an embedded atom model of aluminum [J. Mei and J.W. Davenport, Phys. Rev. B 46, 21 (1992)] for which the melting temperature for the thermodynamic limit is $826.4\pm 1.3$ K—somewhat below the experimental value of 933 K. After reparametrization, the melting temperature of the modified potential is found to be $931.5\pm 1.5\hspace{0.5em}\mathrm{K}.$