Correlated atomic and molecular wavefunctions using limited Gaussian basis sets

Abstract

Calculations have been carried out using limited Gaussian basis sets for some simple atomic and molecular systems to investigate the possibility of obtaining quantities of chemical interest such as vibration frequencies, dissociation energies, and ionization potentials even though imperfect core functions lead to inaccurate total system energy values. The systems which have been studied are He, Li⁺, Be²⁺, Li, Be⁺, Be,H₂, Li⁺₂, Li₂ and LiH. Outer shell electron correlation for Be, H₂ Li₂ and LiH has been included through use of a specific electron correlation term in the wave function. Dissociation energies for H₂, Li₂, and LiH are calculated with errors of 0.20, 0.31 and 0.40 eV.