Ab initio test study of the N2...H2 and N2...He van der Waals dimers

Quantum chemical fully ab initio conformational calculations was performed for the weakly bound van der Waals N-2...H2 and N-2...He dimers in the framework of the supermolecule approach. The counterpoise-corrected interaction energies were computed through fourth order MBPT using basis sets constructed to give accurate values for the electric moments, polarizabilities and dispersion energy contributions. The best size-to-performance ratio basis set found in the present study, predicts the T-shaped structure to be the most stable configuration for N-2...He, with a well depth D-e of 2.68 meV at a minimum distance R-e of 3.44 Angstrom, in close agreement with calculations performed with larger basis sets. The relative stability of the configurations studied for N-2...H-2 were: collinear structure > parallel structure > T-shaped structures. The collinear structure represent the most stable configuration, with a D-e value of 8.35 meV at a equilibrium distance R-e of 7.60a(0). (C) 1999 Elsevier Science B.V. All rights reserved.