THE QUANTUM-MECHANICAL HARTREE-FOCK STAIRCASE METHOD FOR MOLECULAR ELECTRONIC ENERGIES

Abstract

A new method involving highest-occupied Hartree-Fock orbital energies and Hartree-Fock proton removal energies is shown to lead to improvements over the traditional quantum mechanical Hartree-Fock expectation values for total atomic and molecular electronic energies, leading to improvements in molecular dissociation energies, even though only Hartree-Fock wavefunctions are employed. Also, as an alternative to Koopmans' theorem, it is proven that the magnitude of the highest-occupied Hartree-Fock orbital energy would equal the exact ionization energy if the ground-state wavefunction were to contain no singly-excited antisymmetric products with respect to replacement of the highest-occupied Hartree-Fock orbital. Singly-excited antisymmetric products are known to make relatively small contributions to the exact ground-state wavefunction.