Percus-Yevick bridge functions in a thermodynamic self-consistent theory of hard sphere mixtures

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Abstract
Two component hard sphere mixtures are studied by means of a modified hypernetted-chain (MHNC) approach in which Percus-Yevick (PY) bridge functions are employed. The thermodynamic self-consistency of the theory is obtained by using as adjustable parameters the hard sphere diameters entering the expressions of the bridge functions. Thermodynamically consistent calculations are also performed in the Rogers-Young (RY) approximation in terms of two consistency parameters. A wide range of diameter ratios and of relative concentrations of the particle species is explored, with particular attention to strongly asymmetric mixtures in the highly diluted regime of the bigger-sized component. Comparison with Monte Carlo results, and with well known parametrizations of computer simulation data, shows that the MHNC predictions for thermodynamic and structural quantities are generally very accurate and slightly superior to the RY ones. It also turns out that the PY bridge functions, which yield the thermodynamic consistency, reproduce fairly well those of the actual mixture as obtained from the parametrizations of simulation results. Such an agreement remains valid up to diameter ratios as great as 3, and down to 2% concentration of the bigger-sized component.