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All available numerical data on virial coefficients along with simulation results for the compressibility factors of hard body fluids and their mixtures have been compiled. Practically all relevant theories for these fluids (lattice theories, specific methods for discontinuous potentials, integral and integro-differential theories, expansion and resummation techniques, as well as perturbation and conformal theories) are reviewed and their results are compared with the data. The individual methods are critically assessed and their advantages and limits are discussed.

A new equation of state for hard chain moleculesThe formerly proposed equation of state of fused hard-sphere molecules is applied to evaluate the compressibility factor of systems of flexible chains. A fair agreement with the available Monte Carlo data is obtained. Next, the equation of state extended to mixtures is used to predict the P-V-Tbehavior of binary systems composed of simple hard-body chains differing in the number of atoms in molecules. Good accordance of the calculated and pseudoexperimental values-within the experimental errors of the data-is obtained. To get further experimental data for pure chain molecules and their mixtures Monte Carlo simulations were performed for the system of linear tetraatomic molecules with the site-site length 1 * = 1 and their equimolar mixtures with hard dumbbells at several densities.Comparison of the results for the linear tetraatomics with data on the corresponding flexible chain molecule system reveals a good agreement of the data. The proposed equation of state describes adequately the behavior of both the pure fluid and mixtures.

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A theoretical study of the statistical mechanical description of systems composed of non-spherical convex molecules is made. Thermodynamic functions of one-component and multicomponent systems of particles interacting via the pair potential of the Kihara core type are expressed by integrals over the minimum distance between two interacting convex bodies and three angles characterizing the convex body geometry. The approach is applied to the hard convex body system where the averaged contact correlation function is introduced. Exploiting ideas of the scaled particle theory the approximate expressions for the averaged correlation functions are given in terms of the geometric functionals of hard convex bodies.