NA-CL- ION-PAIR ASSOCIATION IN SUPERCRITICAL WATER()

Molecular dynamics simulations of supercritical electrolyte solutions with three different ion-water models are performed to study the anion -cation potential of mean force of an infinitely dilute aqueous NaCl s olution in the vicinity of the solvent's critical point. The associati on constant for the ion pair Na+/Cl- and the constant of equilibrium b etween the solvent-separated and the contact ion pairs are determined for three models at the solvent critical density and 5% above its crit ical temperature. The realism of the aqueous electrolyte models is ass essed by comparing the association constants obtained by simulation wi th those based on high temperature conductance measurements. Some rema rks are given concerning the calculation of the mean-force potential f rom simulation and the impact of the assumptions involved. (C) 1995 Am erican Institute of Physics.