Ab initio theory of the polarizability and polarizability derivatives in H2S

Abstract Ab initio finite-perturbation self-consistent-field (SCF) and configuration interaction (CI) calculations utilizing an extensive basis of cartesian gaussian orbitals are reported for the electric dipole polarizability tensor, α, and the polarizability derivative tensor, α′, of H 2 S. Particular attention was devoted to the selection of an appropriate molecular orbital basis and configuration expansion for determining electron correlation contributions to the polarizability. The common practice of truncating configuration expansions based on a perturbation theory correction to the energy is shown to be inadequate for this property. Contrary to the predictions of such an approach, we conclude that electron correlation has little effect on α and α′ in H 2 S. Our calculation yielded a nearly isotropic polarizability tensor, whose trace, α , is ca. 5% below the experimental result. The magnitude of the derivative ( α ′) along the symmetric stretch is also in good agreementwith experiment. It is positive and roughly an order of magnitude larger than the components along the other two modes. The derivative anisotropy parameter is found to be positive for all three normal modes. Theoretical dipole moment derivatives have also been evaluated and are compared to those determined from the infrared spectrum. Recent data from Rayleigh and Raman scattering experiments on H 2 O are discussed in light of our results for H 2 S.