ON THE LOCAL AND NONLOCAL COMPONENTS OF SOLVATION THERMODYNAMICS AND THEIR RELATION TO SOLVATION SHELL MODELS

A procedure for identifying the local and nonlocal components of exces s partial molar quantities is presented. This procedure is based on an analysis of the excess thermodynamic quantities expressed as integral s of local estimators over the system volume. The local components can be described in terms of the solvation shell model and an independent of the condition of solute insertion. The nonlocal components are rel ated to the asymptotic behavior of distribution functions at large dis tances from the solute and they give rise to the ensemble dependence o f the thermodynamic quantities of solvation. It is shown that in the c onstant pressure process, by using natural choices for the local estim ators, the nonlocal components of the excess partial molar energy, ent halpy, entropy, and volume are absent. The relationship between our an alysis and a phenomenological model which expresses excess thermodynam ic quantities in terms of the solute volume, surface area, and diamete r is also considered and the validity of the local interpretation is d iscussed. (C) 1998 American Institute of Physics.