Self-consistent, nonorthogonal group function approximation for polyatomic systems. II. Analysis of noncovalent interactions

The self-consistent nonorthogonal group function (NOGF) approximation has been reformulated for the calculation and analysis of noncovalent interactions. With the help of perturbation theory it is shown that the present analysis differs from previous decompositions in the polarization interaction, and the source of this difference is exhibited. The method is applied to several H-bonded dimers and one non-H-bonded complex, and the results are compared with previous calculations. At the same time a complete basis set analysis is made for each system and corrected interaction energies and dipole moments are calculated. The relative reliability of the corrected and uncorrected quantities is discussed. The NOGF formalism is used to construct a wave function which accounts for a limited part of the charge transfer effect, and results are presented which show that for medium quality basis sets this wave function may be more reliable for the calculation of interaction properties of H-bonded complexes than the standard SCF–MO wave function.