Effective potentials for 1:1 electrolyte solutions incorporating dielectric saturation and repulsive hydration

Abstract

Implicit water potentials are developed for the study of thermodynamic and structural properties of solutions of NaCl, LiCl, and KCl. The interaction potential between cations and anions is parametrized from the ionic crystal potential. Two short-range corrections were added to the system to account for the water solvent. The first is due to dielectric saturation which reduces the dielectric permittivity in the vicinity of an ion. The second is a repulsive Gaussian potential which represents the first hydration shell around the ions. Grand canonical Monte Carlo simulations were performed to calculate the mean ionic activity coefficients. Molecular dynamics simulations were performed to calculate the radial distribution functions of 1.0 molal solutions at 298 K which were used to compare the structure of the explicit and implicit water simulations. The implementation of dielectric saturation and a repulsive hydration potential results in an excellent description of the mean activity coefficient and is able to capture structural features of contact ion pairs and solvent separated ions.