MANY-BODY SYMMETRY-ADAPTED PERTURBATION-THEORY STUDY OF THE HE...F- INTERACTION

The many-body symmetry-adapted perturbation theory (MB SAPT) has been employed for the calculation of the interaction potential for the He...F- system. At the Hartree-Fock level of the theory the interaction energy is dominated by the Heitler-London type short-range repulsion of the unperturbed monomers and the second-order induction effects. At the correlated level the interaction energy is the sum of equally important attractive and repulsive contributions: electrostatic-correlation, exchange-correlation, and dispersion energies. The correlation component amounts on the average to about 10% of the total interaction energy and for most internuclear separations increases the absolute value of this energy. Our potential has a minimum at R(m) = 6.65 bohr with the interaction energy epsilon(m)=-0.255 mhartree, in good agreement with the existing ab initio supermolecular data. Our results differ considerably from those predicted by recently introduced semi-empirical and empirical models of the rare-gas atom-halogen-ion interactions. The analysis of the individual components of the (semi-)empirical potentials show that the induction and dispersion parts agree very well with the ab initio MB SAPT results, while the short-range repulsion energy is largely underestimated.