The repulsive wall of the Tang-Toennies potential for He₂ reexamined

Abstract

In the case of He₂, Aziz et al. [Z. Phys. D 21,251 (1991)] proposed a modification to the original Tang-Toennies potential form (TT) [J. Chem. Phys. 80, 3726 (1984)] which allows for a more accurate repulsive wall. The total interaction energyE _int can, in principle, be considered as the sum of uncorrelated and correlated energies, i.e.E _int (r)=E _unc(r)+E _c (r).E _unc is represented by the (SCF) Hartree-Fock interaction energyE _SCF for the rare gas dimer.E _c , which is expressed in terms of ab initio dispersion coefficients and a suitable damping function to account for charge overlap effects, is dominated by the van der Waals attraction in the long range. While the other literature potentials reproduce some of the data, only the TT model as modified by Aziz et al. properly characterizesE _int over the entire range andE _SCF over its range of significance.