Behavior of the aqueous sodium chloride solution from molecular simulations and theories

Molecular simulations and theories are important tools for studying electrolyte solutions. In this work, molecular dynamics simulations with one of the most widely used force field combination of water and alkali and halide monovalent ion parameters were first conducted for the aqueous sodium chloride solutions to predict density, self-diffusion coefficients and molar conductivity. Then the radial distribution functions were analyzed to obtain the first shell solvation radii and coordination numbers of ions, which are found practically unchanged against concentration. Together with the ion force field parameters, they were further applied into various molecular theories to predict the Gibbs energy of solvation, static relative permittivity, mean ionic activity coefficients and molar conductivity. It is remarkable to see that the mean ionic activity coefficients and molar conductivity can be predicted with deviations of 1.1% and 1.4%, respectively, up to 6 mol/kg-H₂O.