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

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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.