Valence electron studies with Gaussian-based model potentials and Gaussian basis functions. III Applications to two-valence-electron systems composed of combinations of Li, Na, H, or their unipositive ions

Abstract

A previously developed simple valence‐only electronic structure theory based on atomic core model potentials and using flexible Gaussian valence basis functions is applied to the two‐valence electron systems Li₂, Na₂, NaLi, LiH, NaH, Li₃⁺, Na₃⁺, Li₂Na⁺, LiNa₂⁺, LiH₂⁺, Li₂H⁺, NaH₂⁺, Na₂H⁺, and H₂, within the SCF MO model. Results for calculated equilibrium geometries and energy changes for certain chemical reactions are compared to the corresponding quantities from analogous all‐electron ab initio calculations. The model potential results are quite similar to those from the ab initio ones and are generally satisfactory for such a simple theory. There is a tendency toward slightly long internuclear distances (average deviation of all unique independent distances is +0.06 bohr) and slightly high energy of complex relative to separate constituents (average deviation of dissociation reaction energies is −2.1 kcal/mole) in these calculations relative to the all‐electron ones, the explanation of which will require future detailed analysis of both the model potential valence‐electron and the ab initio all‐electron calculations.