Solvation many-body interaction terms

While proper treatment of intermolecular interactions is very important, it should be remembered that entropy has a crucial role in the structure of condensed phases. Hydropho-bicity, e.g., is an entropy-driven effect and is intrinsically many-body in nature. One of the simplest solvation models envisages the solute as filling a cavity in a hard-sphere (i.e., billiard-bair like, without any attractive intermolecular interactions) fluid. Entropy-driven packing of the solvent around the solute results in a liquid structure and it is often helpful to represent this structure in terms of a potential of mean force, a fictitious intermolecular interaction constructed to mimic, in a hypothetical entropy-free world, the actual liquid structure. 

---