A contribution to the solvation free energy in isotropic and anisotropic polarizable continuum model.

A general formalism for the calcn. of cavitation energies in the framework of the scaled particle theory has been implemented in the Polarizable Continuum Model (PCM), contributing to the nonelectrostatic part of the mol. free energy in soln. The solute cavity and the solvent mols. are described as hard spherocylinders, whose radius and length are related to the actual mol. shape, while the solvent d. is estd. from exptl. data, or from the solvent mol. vol., suitably scaled. The present model can describe isotropic solns. of spherical and rod-like mols. in spherical or rod-like solvents, and also anisotropic solns. in which the solvent mols. are oriented in space: in this case, the cavitation energy also depends on the relative orientation of solute and solvent mols. Test calcns. have been performed on simple systems to evaluate the accuracy of the present approach, in comparison with other methods and with the available exptl. ests. of the cavitation energy, giving encouraging results.