A simple predictive model of chemical potentials: H2(1Σg) and Li2(1Σg)

A simple model for van der Waals potentials presented earlier [J. Chem. Phys. 80, 3726 (1984)] has been extended to describe chemical bonds by including the exchange-dispersion term of Herring and Flicker. For H2, the 1Σ ground state potential is predicted in excellent agreement with the accurately known ab initio potential, the well depth being reproduced to within 0.6%. New two configuration self-consistent-field (SCF) calculations for the 1Σ and the 3Σ states of Li2 have made it possible to test the model for this system as well. Here the discrepancy is only 3% in the well depth for the 1Σ Li2 potential