A molecular approach to the formation of KCl and MgCl + ion-pairs in aqueous solution by density functional calculations

Abstract

Full geometry optimizations have been carried out on molecular models of [M(H 2O) 6] n+ , [M(H 2O) 6…H 2O] n+ and [M(H 2O) 6…Cl] ( n−1)+ (M=K and Mg, n=1 for K and 2 for Mg) using the density functional methods. The optimized geometries of [K(H 2O) 6] + and [Mg(H 2O) 6] 2+ were a regular octahedron. In the optimizations of [M(H 2O) 6…H 2O] n+ and [M(H 2O) 6…Cl] ( n−1)+ , the octahedral structures of [M(H 2O) 6] n+ units were completely broken for K + complexes and almost kept for Mg 2+ complexes. The results have been discussed in connection with the formation of KCl and MgCl + ion-pairs in aqueous solutions.