Molecular closure approximations molecule fluids

The strategy for explicitly formulating the molecular closures was guided by three considerations." (1) Use of the commonly employed reference approach. The successful site-site PY closure is retained to describe the repulsive force reference fluid but a molecular closure scheme is adopted to describe the attractive, slowly varying forces. (2) The approximation scheme is required to provide an exact description of the structural consequences of the tail potentials at the two-molecule level in the weak coupling limit [/3umm-W 1]- (3) Use of an appropriate site-site approximation for the direct attractive interaction contribution motivated by experience in simple fluids. ... 

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