Molecular closure approximations structure

Structure and the molecular closure approximations. Very recent work by Gromov and de Pablo has shown for the symmetric blend model that PRISM with the R-MPY closure is in excellent agreement with continuous space simulations for the structure, mixing thermodynamic properties, and the coexistence curve. 

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. ... 

The effect of attractions on the structure of dense one-component polymer melts. According to the van der Waals ideas, attractions should have very little effect. Surprisingly, we are unaware of simulations that have probed this question, although they are now in progress. Recent PRISM studies by Butler and Schweizer using atomic and molecular closures have been carried out. Repulsive force screening of the effects of attractions on structure is recovered for many, but not all, closure approximations. 

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