Molecular-Orbital Theory for Infinite Systems: Self-Consistent Field Perturbation Treatment of Hydrogen-Bonded Molecules

Abstract

A self-consistent field perturbation theory of intermolecular interactions is introduced with a view to its application to the study of hydrogen-bonded molecular crystals. A numerical perturbation scheme is also introduced that permits a very detailed numerical check to be made on both the perturbation equations and the corresponding computer program. From a numerical study of the (HF)2 and (HCN)2 systems it is shown that, if taken to the third order, the perturbation method yields dimerization energies and changes in charge densities to within 7% of the values obtained by direct calculations. Structural data calculated from perturbation theory are still more accurate.