Inclusion of core-valence correlation effects in pseudopotential calculations. I. Alkali atoms and diatoms

Abstract

A simple procedure is developed to include the core‐valence polarization and correlation effects in small metallic clusters of alkali atoms. The fluctuation of the electric field on the polarizable core, as calculated from optimized limited valence basis sets, plays the dominant role. The atomic ionization potentials and the ground state spectroscopic characteristics of Na₂, K₂, Cs₂, and of their positive ions are significantly improved. The method is applicable to polar compounds as well, as illustrated through a study of CsH. The relationship between the present procedure and Bardsley’s −α_D/2 (r²+d²)² potentials is discussed.