Weeks-Chandler-Andersen system functions

The cluster expansions in this section are of the most primitive kind in the sense that they give A and the correlation functions relative to the corresponding functions for a reference system of noninteracting particles. Stell and Lebowitz have shown how to carry analogous procedures through for arbitrary reference systems, such as a suitable assembly of hard spheres. Other resummations and optimizations aimed at achieving better convergence of cluster series have been studied intensively by Andersen, Chandler, and Weeks. ... 

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