SYMMETRY-ADAPTED PERTURBATION-THEORY FOR THE CALCULATION OF HARTREE-FOCK INTERACTION ENERGIES

A symmetry-adapted perturbation theory is formulated for the calculati on of Hartree-Fock interaction energies of closed-shell dimers. The pr oposed scheme leads to a basis-set-independent interpretation of the H artree-Fock interaction energy in terms of basic concepts of the theor y of intermolecular forces: electrostatics, exchange and induction. Nu merical results for different geometries of He-2, Ne-2, He-C2H2, He-CO , Ar-HF, (HF)(2) and (H2O)(2) complexes show that in the region of the van der Waals minimum the proposed perturbation theory reproduces acc urately the Hartree-Fock interaction energy. This fast convergence and relatively small computational cost of the proposed perturbation sche me suggest that this method is a practical alternative for the standar d supermolecular approach.