Potential energy surfaces for simple chemical reactions: Li + F2 → LiF + F

A potential energy surface is calculated for the Li + F₂ → LiF + F reaction using an ab initio multistructure valence-bond approach. The orthogonalized Moffit (OM) method is employed to apply a correction for the large errors made by the ab initio calculation in representing the F⁻ ion relative to the F atom. The OM method predicts the potential surface to be of the highly “attractive” or “early downhill” type and to possess a potential energy well with respect to dissociation to the products LiF + F. The attributes of the surface predicted by the OM method are compared with those suggested by experiment and used in trajectory calculations for analogous systems.