Toward a General Formulation of Dispersion Effects for Solvation Continuum Models

We revised the quantum model of Amovilli and Mennucci (J. Phys. Chem. B 1997, 101, 1051) to include the dispersion contribution to the solvation free energy within the framework of continuum models. Our revised formulation makes use of a single adjustable solvent dependent parameter, and it can be readily generalized to different quantum mechanical descriptions. In particular, we made use of DFT and applied the model to investigate dispersion effects on vertical excitation energies within a time-dependent DFT framework. Our findings show that dispersion effects constitute a significant component of the absolute solvent effect but when relative solvent-solvent shifts are considered a cancellation effect is observed