MOLECULAR VERSUS ATOM-ATOM INTERACTION ANISOTROPY IN THE CASE OF THE AR-N-2 VAN-DER-WAALS SYSTEM

The potential energy surface of the ArN2 van der Waals complex is dete rmined with high-level ab initio calculations, confirming the single w ell in the T-shaped configuration, predicted with empirical potentials . In the context of analytical representation of the potential, two di fferent schemes for treating the atom-diatom interaction are compared, with the anisotropy introduced for the total molecular component and for its constituent atoms. The latter way is found to provide better p redictions for the potential energy surface in terms of the same amoun t of input information, particularly if the latter is very limited, an d thus presents a useful alternative to the traditional Legendre polyn omial expansion. Comparison with empirical potentials reveals a signif icantly lower anisotropy of the ab initio potential. The Ar-N-2 surfac e obtained is used to predict the structure and stability of larger Ar nN2 (n greater than or equal to 2) clusters.