Dielectric response of solvent surrounding an ion pair: Ewald potential versus spherical truncation

The solvent dielectric response has been evaluated for a system of two oppositely charged ions in aqueous solution. When the Ewald potential is used to model the long-range interactions, the correct high dielectric shielding of the ions by the water is obtained by either of two methods; from the ion charging free energies, or the slope of the ion-ion potential of mean force in the asymptotic region. In contrast, simply truncating the Coulomb interactions leads to unphysical dielectric behavior.