Investigation of the interaction between molecules at medium distances: I. SCF LCAO MO supermolecule, perturbational and mutually consistent calculations for two interacting HF and CH 2O molecules

Abstract

Two interacting HF and CH 2O molecules have been treated at medium (3.20 A) intermolecular distances at one common supermolecule using the ab initio SCF LCAO MO method, and their interaction energies have also been calculated with the aid of a perturbational scheme of Murrell. Randic and Williams which takes into account overlap effects. In addition to these, mutually consistent calculations have been performed for the mentioned pairs of molecules obtained simultaneously the electrostatic and polarization parts of their interaction energies. The proposed model gives somewhat better results than the perturbational one in the monopole approximation. Finally, it is discussed how the model could be improved to obtain rather good interaction energies at medium distances without performing an expensive supermolecule calculation or calculating all the intermolecular integrals occurring in the perturbational approach.