The effect of water models on the interaction of the sodium–chloride ion pair in water: Molecular dynamics simulations

We present a comparative study of the potentials of mean force (PMF) of the sodium–chloride ion pair in the simple point charge (SPC and SPC/E) water models using thermodynamic perturbation theory and the molecular dynamics technique. In agreement with previous studies, the PMF’s display two minima corresponding to the contact and solvent-separated ion pairs. However, the contact and solvent-separated regions are of comparable importance for the SPC water model, whereas the solvent-separated region is favored over the contact region for the SPC/E water model.