A FLUCTUATION APPROACH TO SOLVATION IN POLAR FLUIDS

A phenomenological approach to solvation in polar fluids is proposed that explicitly recognizes the role of thermal fluctuations in the solvent. The probability distributions for the fluctuating electric potential, field, field gradient, etc. in a polar fluid are shown to be Gaussian with a variance determined by the linear (dielectric) response function of the fluid. This Gaussian distribution is used to calculate the solvation free energy of a solute carrying a permanent multipole and/or a polarizability. Unlike the traditional reaction-field approach, the fluctuation approach can describe the solvation of a polarizability by the fluctuating field from the solvent. This contribution to the solvation free energy may be regarded as the zero-frequency part of the electrodynamic dispersion interaction.