Entropy and Molecular Correlation Functions in Open Systems. II Two- and Three-Body Correlations

We consider the contributions from the correlation of pairs and triples of molecules to the configurational entropy per molecule of a simple fluid system. Using numerical values of the pair function and only certain moments of the triplet function, we have computed the first few terms in an expression for the entropy in terms of the correlation functions. The results, which compare favorably with experimental values over a range of densities including that of the liquid, indicate that contributions from the correlations of triples of molecules can be appreciable. The computations are done for a fluid of hard spheres and liquid neon and the results are discussed in terms of the molecular correlations in a simple fluid.