Local polarizabilities and dispersion energy coefficients

Static and dynamic polarizabilities of atoms and functional groups within molecules are calculated from the response of the distributed multipoles to different applied potentials, using a newly developed localization scheme. The methodology, described here in full for the first time, is based entirely on first-principles calculations. It gives physically reasonable and transferable polarizabilities and dispersion energy coefficients, for multipole components up to at least octopole. Polarizabilities and dispersion energy coefficients determined using this method are used to calculate induction and dispersion energies which are compared with ab initio energies calculated at the Coupled Hartree-Fock level of theory. The localized polarizabilities and dispersion energy coefficients are shown to be an improvement over the corresponding molecular values, in terms of both absolute accuracy as well as convergence properties.