Theory of supercooled liquids and glasses for binary soft-sphere mixtures via a modified hypernetted-chain integral equation.

Abstract

We discuss the equilibrium properties of highly supercooled binary soft-sphere fluids by a modified hypernetted-chain (MHNCS) equation proposed recently by us. The MHNCS approximation is made by a proper interpolation of the bridge functions of the Percus-Yevick hard-sphere model and the leading term of the elementary diagrams that were first successfully applied to classical one-component plasmas. The MHNCS approximation has been found to work well for one-component soft-sphere fluids above and below the freezing point. For a more crucial test, the MHNCS equation is extensively studied for the binary soft-sphere fluids. We have obtained numerical solutions of the MHNCS equation for a binary mixture of the 12th-inverse power potential with different core diameters. These results are compared with those of computer simulations and the Rogers-Young approximation. Below the freezing temperature, the solution of the MHNCS equation reproduces a splitting of the second peak of the pair distribution function (PDF) for various core size ratios, compatible with the computer simulations. Using the PDF thus obtained, thermodynamic and structural properties of the highly supercooled binary soft-sphere fluids are investigated.