INTERIONIC POTENTIALS OF MEAN FORCE FOR SRCL2 IN POLARIZABLE WATER - A COMPUTER-SIMULATION STUDY

Potentials of mean force (PMFs) and solvation properties of SrCl2 in p olarizable water have been studied using molecular dynamics simulation s. The PMF between isolated Sr2+ and Cl- ions involves a stable contac t ion-pair state with a binding free energy of -1.8 kcal/mol and a dis sociation barrier of 3.5 kcal/mol. A solvent-separated state is observ ed to have comparable free energy and a minimal barrier for dissociati on to free ions. The PMF between a second Cl- ion and the Sr2+...Cl- c ontact ion pair has also been calculated. The Cl-...Sr2+...Cl- complex is nonlinear and involves a bridging water molecule strongly hydrogen -bound to both chlorine ions.