AB-INITIO MOLECULAR-ORBITAL CALCULATIONS ON ION-PAIR WATER COMPLEXES OF METAL-HALIDES AND OXIDES

Ab initio MO calculations are performed on a series of ion-molecular a nd ion pair-molecular complexes of H2O + MX (MX = LiF, LiCl, NaCl, BeO and MgO) systems. BSSE-corrected stabilization energies, optimized ge ometrical parameters, internal force constants and harmonic vibrationa l frequencies have been evaluated for all the structures of interest. The trends observed in the geometrical parameters and other properties calculated for the mono-hydrated contact ion pair complexes parallel those computed for the complexes of the individual ions. The bifurcate d structures are found to be saddle points with an imaginary frequency corresponding to the rocking mode of water molecules. The solvent-sha red ion pair complexes have high interaction energies. Trends in the i nternal force constant and harmonic frequency values are discussed in terms of ion-molecular and ion-pair molecular interactions.