Core-valence correlating basis sets for alkali and alkaline earth metal atoms

For 12 alkali and alkaline earth metal atoms from Li to Ra, contracted Gaussian-type function sets are developed for the description of correlations among the (n-1) s, (n-1) p, and ns electrons, where n is the principal quantum number of the outermost shell. A segmented contraction scheme is employed for the compactness and efficiency. Contraction coefficients and exponents are determined so that the deviation from accurate natural orbitals of the ground states is minimized. For heavy atoms from Cs to Ra, the spin-free relativistic effects are considered through the third-order Douglas-Kroll approximation. To test the present correlating sets, all-electron calculations are performed for the ground state of 12 diatomic hydrides, 6 alkali metal dimers, 4 alkaline earth metal oxides, and 12 diatomic fluorides. The calculated spectroscopic constants are in excellent agreement with the experimental values.