ON THE ADEQUACY OF PAIRWISE ADDITIVE POTENTIALS FOR RARE GAS-HALOGEN SYSTEMS - THE EFFECT OF ANISOTROPY OF INTERACTIONS BETWEEN ATOMS

A simple model is presented for the potential energy functions of rare gas dihalides RgX(2), which uses empirical potentials for diatomic fr agments and takes properly into account anisotropic interactions betwe en atoms, resulting in diabatic potentials which correlate with the gr ound state X(2) molecule and Rg atom. Specific results are obtained fo r potential energy surfaces of ArX(2) (X = F, Cl, Br, I) complexes and compared to those from several widely used models based on pairwise a dditive isotropic interactions. All these earlier models are found to underestimate the binding in the linear geometry, predicting a complet e absence of a linear bound state; this feature is especially signific ant for ArF2 in which the anisotropic model predicts the linear config uration to be more stable. The new anisotropic model leads to Ar-X(2) dissociation energies in good agreement with experiments. (C) 1995 Ame rican Institute of Physics.