Theoretical Study of Lithium-Fluoride and Lithium-Chloride Ion Pairs in Aqueous Solution. An SCF-CNDO/2 Approach Including Continuum Solvent Effects

Abstract

SCF-CNDOI2 ealculations, including solvent effeets via an extended version of the Generalized Born Formula (GBF), have been performed for LiX(H20) speeies (n = 1,2; X = F, CI). Several minima in the free energy surfaee, representing intimate and solvent-separated ion pair struetures, have been analyzed. Qualitative results show a preferential stabilization of the intimate forms with respeet to the solvent-separated ones. The results are diseussed on the basis of a eonvenient partition of lhe total solute-solvent free energy. The interaetion of the ionie species with the bulk solvent negleeted in previous studies appears to be responsible for the preferential stability of the intimate forms.