Statistical Mechanics of Phase Diagrams. I. Inverse Power Potentials and the Close-Packed to Body-Centered Cubic Transition

Abstract

Most of the softer metals exhibit a low-temperature close-packed phase, an intermediate-temperature body-centered phase, and a high-temperature fluid phase. Here we relate this behavior to that of theoretical model systems in which particles interact with the inverse power potential φ (r)=ε ( σ / r)n. We show that the same three-phase behavior occurs for the models provided that the interparticle repulsion is sufficiently soft (n ≤ 7). For the model systems the phase boundary between the close-packed and the body-centered phases is located using lattice dynamics. The fluid—solid melting line is deduced from Monte Carlo computer experiments.