Integral equation and computer simulation study of the structure of additive hard-sphere mixtures

The Percus-Yevick (PY), hypernetted chain (HNC), and Martynov-Sarkisov (MS) closures for the Ornstein-Zernike equation are used to calculate the pair distribution functions of binary additive hard-sphere mixtures. The theoretical results are compared with new precise Monte Carlo simulation data described herein. Generally, the agreement of the MS closure with the data is the best and that of the HNC closure the worst. At some state points deviations from the simulation data are several times larger than those for pure hard spheres at the same packing fractions. An unusual behaviour pattern of the distribution functions has been found for systems with a hard sphere diameter ratio of 0.3, at low concentrations of the larger spheres. Unexpected minima and maxima in g(ij)(r) appear at distances r similar to sigma(ij) + sigma(22), where sigma(22) denotes the diameter of smaller spheres. The phenomenon seems to be related to the predominance of certain geometrical arrangements of the component spheres.