Ab initio calculations of multipole moments, polarizabilities and isotropic long range interaction coefficients for dimethylether, methanol, methane, and water

Abstract

Multipole moments, up to and including l = 6, and multipole polarizabilities up to and including l + l′ = 6, have been calculated, for the molecules dimethylether, methanol, methane and water, from LCAO-SCF wavefunctions using an AO basis set of DZ quality augmented with double d-polarization functions at the non-hydrogen-, and p-polarization functions at the hydrogen atoms. The polarizabilities were obtained using Rayleigh-Schrödinger perturbation theory and the non-empirical Unsöld method. The long range isotropic coefficients, C ₆, C ₈, and C ₁₀ have been calculated for all ten types of interactions between the four molecular species. For the interaction between like molecules an effective C ₆ coefficient has been derived for comparison with experiment. The agreement between calculated values and experimental data, as far as available, is satisfactory.