Extension of the Hartree-Fock Plus Dispersion Method by First-Order Correlation Effects

The Hartree-Fock plus dispersion (HFD) method for calculations of intermolecular interaction energies has been extended by the addition of the correlation part of the first-order interaction energy computed form Kohn-Sham determinants of monomers. This extension increases the computational requirements of the HFD approach only insignificantly and at the same time reduces the uncertainties of the interaction energies several times for most of the investigated systems. Thus, the proposed method becomes an attractive computational tool for investigating interactions of very large molecules at the HF-level costs.