CALCULATION OF THE DISPERSION ENERGY CONTRIBUTION TO THE SOLVATION FREE-ENERGY

A general expression for the dispersion energy contribution to the solvation free energy is derived by exploiting the analogy between certain aspects of the theory of intermolecular forces and of the theory of solvation in the polarizable continuum model. The proposed method of calculation requires a knowledge of the solvent dielectric constant at imaginary frequencies, often efficiently approximated in terms of simple experimental data such as refractive index and ionization potential, and molecular transition densities and energies obtained by standard ab initio methods. By way of examples, the dispersion contribution is calculated for the systems CH4, NH3, H2O, HF and Ne in water as solvent.