Intermolecular interactions: Reproduction of the results of ab initio supermolecule computations by an additive procedure

Abstract

An additive systematics for the rapid computation of intermolecular interactions has been worked out. The interaction energy is computed as a sum of four components. The electrostatic component is obtained by using the overlap multipole expansion of the SCF density distribution of the isolated ligands, and the other components (polarization, dispersionlike, and repulsion) have been calibrated in order to reproduce the results of ab initio SCF computations on the systems Na+—H2O, K+—H2O, H2O—H2O, and NH4+—H2O. A series of cation-ligand interactions is then investigated with this systematics, and the results, compared with the corresponding ab initio SCF ones, are seen to reproduce satisfactorily both the values of the interaction energies and the essential features of the binding.