Comparison Among Solvent Electrostatic Potentials and a Proposal for Improving the Polarizable Continuum Model

The polarizable continuum model (PCM) is a widely used solvation model. Although the computational cost of the PCM is low, significant energy errors tend to arise when dealing with charged solutes. We focused on solute-solvent electrostatic interactions and investigated the reaction field distribution. By comparing the reaction field in the PCM with those in other solvation models, such as the molecular dynamics and three-dimensional reference interaction site model, we clarified four PCM features that should be modified: the gradient of the reaction field is very small in water; the position of the reaction field representing hydrogen bonds involving solute protons is shifted; the reaction field peaks representing hydrogen bonds involving solvent protons are merged; and the solute-solvent electrostatic interaction energy is overestimated, especially for anions. These features indicate that modifying the PCM by simply retuning existing parameters is difficult. This study lays the groundwork for developing of subsequent reaction field correction methods.