Atom-bond pairwise additive representation for halide-benzene potential energy surfaces: an ab initio validation study.

The detailed knowledge of the basic aspects of molecular interactions and the representation of the involved potential energy surface in a proper analytical form are of paramount importance either to elucidate the nature of noncovalent interactions or to perform meaningful molecular dynamics simulations. To this aim, a recently developed semiempirical method, formulated in terms of atom/ion-molecular bond interactions, has been extended to investigate X(-)-C(6)H(6) systems (X = F, Cl, Br, I) and tested against highly correlated MP2 ab initio calculations. The role of the various components to the total interaction energy was also addressed by comparing the semiempirical contributions to their MP2 counterparts calculated using the symmetry adapted perturbation theory. The overall results, besides providing a more detailed picture of the interaction between anions and aromatic systems, pointed out that the current model is able to reproduce remarkably well the main features of the potential energy surface for the heavier X(-)-C(6)H(6) systems (X = Cl, Br, I), whereas for fluoride-benzene, the binding energies are underestimated as a consequence of the failure of the semiempirical method to describe the electrostatic interaction between a diffuse anion and a benzene at short range by means of a simple point charge model.