Time-dependent Hartree-Fock calculations of dispersion energy

A new method of computing intermolecular dispersion energies, starting from the SCF wavefunctions of the separate systems, is discussed and illustrated. The method is based on the use of generalized frequency-dependent polarizabilities, calculated using TDHF (time-dependent Hartree-Fock) theory, and all ‘self-consistency’ effects are thus accounted for in the final expressions for the dispersion energy. No multipole expansions are required. The method is shown to be computationally efficient in test calculations of the dispersion interactions between helium atoms and between hydrogen fluoride molecules.