Fifth virial coefficient of a two-component mixture of hard discs

The fifth virial coefficient is computed of a binary mixture composed of different-size hard discs with additive diameters. The irreducible cluster integrals are evaluated numerically using the Monte Carlo method. As for a hard-sphere mixture in three dimensions (F. Saija, G. Fiumara, and P. V. Giaquinta, 1996, Molec. Phys., 89, 1181), it is found that the fifth virial coefficient becomes slightly negative in the regime of high dilution of the larger-disc component when the diameter ratio of the two species is lower than 0.2