A simple theoretical model for the van der Waals potential at intermediate distances. I. Spherically symmetric potentials

A simple potential model is presented, which uses available ab initio calculated short range SCF Born–Mayer parameters and the perturbation theoretical dispersion terms for the long range potential. In the intermediate region two corrections are shown to be necessary to take account of the divergence of the dispersion expansion and the influence of electron overlap. These corrections can be predicted from the known asymptotic parameters and atomic properties. The resulting potential model, which contains only seven potential parameters, is shown to predict the van der Waals potential parameters R0[V (R) =0], Rm (well location), and ε (well depth) for six rare gas–rare gas atom combinations and six open shell–rare gas atom combinations. The predicted potential shape for Ar–Ar is in excellent agreement (≲3%) with the best experimental determination. The model is used to predict Born–Mayer parameters from measured values of Rm and ε.