Thermodynamics and kinetics of ion speciation in supercritical aqueous solutions: a molecular-based study

Molecular simulation of infinitely dilute NaCl aqueous solutions are performed to study the Na+/Cl- ion pairing in a polarizable and a non-polarizable solvent at supercritical conditions. The simple point charge (SPC), the Pettitt-Rossky and the Fumi-Tosi models for the water-water the ion-water, and the ion-ion interactions are used in the determination of the degree of dissociation, its temperature and density dependence, and the kinetics of the interconversion between ion-pair configurations in a non-polarizable medium. To assess the effect of the solvent polarizability on the stability of the ion-pair configurations we replace the SPC by the polarizable point charge (PPC) water model and determine the anion-cation potential of mean force at T-r=1.20 at rho(r)=1.5. (C) 1998 Elsevier Science B.V. All rights reserved.