Virial coefficients of hard-sphere mixtures

The fourth and fifth virial coefficients of binary hard-sphere mixtures have been calculated for size ratios $R>~0.05$ and $R\equiv {\sigma }_{22}/{\sigma }_{11}.$ The composition independent partial virial coefficients have been expressed in terms of the Mayer diagrams. The corresponding modified star diagrams were evaluated by Monte Carlo integration. The results are compared with predictions of the Boublik [J. Chem. Phys. 53, 471 (1970)] and Mansoori et al. [J. Chem. Phys. 54, 1531 (1971)] equation of state, and the excellent agreement gives strong support to the validity of that equation of state for very asymmetric mixtures.