Generalized virial expansions

A new simple derivation of the virial expansions for spatial two-particle correlation functions of molecular fluids is given. There is a separate description of short- and long-range interactions. The correlation functions for the short-range interactions are assumed to be known and therefore act as a reference system. Long-range interactions are screened—with the without consideration of the structure factors of the reference system. We give an explicit account of the expansions up to the fourth cluster coefficient. A system of integral equations is derived for the correction terms in the cluster expansions in the different cases. By introduction of approximate closure relations of the RHNC, or similar type, effective numerical solutions are obtained.