Physics of solvation

Calculations are presented of the energetics of an impurity (atom or ion) interacting with a fluid. Two possible configurations are considered: a surface state and a solvated state. For two distinct model problems which we consider (any classical fluid and superfluid helium) we find a common behaviour: the value of a dimensionless parameter lambda determines the relative stability of the surface and solvated states. For lambda greater (less) than 1.9, the sovated (surface) stare is favored, A more realistic estimate for a classical fluid is lambda similar to 1. Predictions are made of a universal solvation behaviour derived from the law of corresponding states. Results are presented for the solvated fraction as a function of cluster radius and temperature. Quantum corrections and the kinetics of solvation are discussed briefly.