Gaussian basis sets foty use in correlated molecular calculations . IV .

An accurate description of the electrical properties of atoms and molecules is critical for quantitative predictions of the nonlinear properties of molecules and of long-range atomic and molecular interactions between both neutral and charged species. We report a systematic study of the basis sets required to obtain accurate correlated values for the static dipole (ar,), quadrupole ((Ye), and octopole ((rs) polarizabilities and the hyperpolarizability ( y) of the rare gas atoms He, Ne, and Ar. Several methods of correlation treatment were examined, including various orders of Moller-Plesset perturbation theory (MP2, MP3, MP4), coupled-cluster theory with and without perturbative treatment of triple excitations [CCSD, CCSD(T)], and singles and doubles configuration interaction (CISD) . All of the basis sets considered here were constructed by adding even-tempered sets of diffuse functions to the correlation consistent basis sets of Dunning and co-workers; With multiply-augmented sets we find that the electrical properties of the rare gas atoms converge smoothly to values that are in excellent agreement with the available experimental data and/or previously computed results. As a further test of the basis sets presented here, the dipole polarizabilities of the Fand Clanions and of the HCI and NZ molecules are also reported.