Semiempirical Potential Energy Functions. I. The H2 and H2+ Diatomic Molecules

After setting up certain theoretical criteria for a semiempirical potential energy function, two such functions for H2+ and H2 are constructed, the simplest of which has the form V=e-aR(e2R−b),where V is the potential energy with its zero corresponding to infinite separation. R is the internuclear distance, e the electronic charge, and a and b parameters. This function is used to correlate the experimental quantities: dissociation energy, equilibrium internuclear distance, force constant, third and fourth derivatives of V with respect to R, united atom energy, and critical distance. A more complicated function is also presented which with one molecular parameter fixed by the dissociation energy is capable of then predicting internuclear distance and force constant.