Molecular hyperpolarizabilities. II. A correlated study ofH2O

Abstract

Correlated calculations using many-body perturbation theory and good basis sets for the dipole moment, polarizability, and hyperpolarizabilities of ${\mathrm{H}}_2$O are reported. The finite-field coupled Hartree-Fock (CHF) theory is used as a zeroth-order approximation, with electron correlation included via the linked-diagram theorem. Single-, double-, and quadruple-excitation contributions are included. It is found that correlation changes $\left|\beta \right(\omega =0\left)\right|$ by about 50% compared to the CHF result. Even larger changes are found among the components of $\overleftrightarrow{\gamma }$. The dependence of the $\overleftrightarrow{\beta }$ hyperpolarizability on geometric displacements is investigated, finding that $\overleftrightarrow{\beta }$ can be highly sensitive to slight changes in bond lenghts.