6533b7d9fe1ef96bd126c0ac

RESEARCH PRODUCT

Phase Diagrams of Alloys and Adsorbed Monolayers: Some Recent Results

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We discuss some recent work done on the calculation of phase diagrams of models of binary alloys and adsorbed monolayers. For the nearest-neighbor Ising antiferromagnet on the fcc lattice (model for the Cu-Au system) we study a rather large lattice of 4 x 643 spins. This is necessary since the inherent frustration of the lattice induces a very small interfacial tension between ordered domains. We find no indications for the suggested L′ phase, and locate the triple point at a nonzero temperature. There is some numerical evidence that it might in fact be a multicritical point. We then discuss the extension of lattice gas models to “elastic lattice gases” (ELGs) which include also translational degrees of freedom. Special attention is paid to the statistical treatment of vacant sites, and it is shown that a system A + vacancies is no longer equivalent to a system A + B. The ELG Hamiltonian is then studied for three-dimensional models on the diamond lattice for the unmixing of semiconductor alloys (where we find Mean-Field-like critical behavior), and for a two-dimensional model for c(2 x 2) structure formation.