Anion electric field is related to hydration energy

Electronic structure calculations that utilize dielectric continuum theory to mimic solvent often considerably underestimate the magnitudes of anion solvation energies in water, unless unphysically small cavities are utilized. It is found that a simple correction term can account for most of this error, while retaining cavities of physically reasonable size for evaluating the bulk dielectric contributions. This correction is based on linear correlation with the minimum value of the outgoing normal electric field produced by the anion on the surface of the dielectric cavity separating it from solvent. Values of the correlation parameters vary somewhat among different chemical classes of anions and are probably related to strong hydrogen bonding interactions between the anions and first-shell water molecules that are otherwise difficult to describe with dielectric continuum theory alone.