Quasiclassical trajectory study of the H + ClF → F + HCl, Cl + HF and F + HCl → Cl + HF reactions and their deuterium isotope variants on a new ( 2A') ab initio potential energy surface

Résumé

In this work we present a 3D quasiclassical trajectory (QCT) study of the H + ClF → F + HCl (1), Cl + HF (2) and F + HCl → Cl + HF (3) reactions on a recent ab initio ground ²A' potential energy surface, mainly for reactants at 300 K. Rate constants, vibrational and rovibrational distributions, angular distributions and mean energy fractions disposed into products were analysed. Deuterated reactions were also considered. Internal distributions were in close agreement with the experimental data, especially for reactions (1) and (3). Reaction (2) exhibited major discrepancies due to the existence of a double microscopic mechanism, direct or migratory plus insertion, which gives rise to very different reaction attributes in each mechanism. The migratory collisions, which are favored by the van der Waals minima, correlate with large impact parameters, produce mainly forward scattering, and furnish a high internal excitation of the products. The direct collisions show exactly the contrary behaviour. In general, the calculated reaction properties can be accounted for in terms of the known L + HH and H + LH dynamics (L: light and H: heavy). QCT rate constants agree very well with experimental data, and a small isotope effect (i.e. k(H)/k(D) < 2) is found for the three reactions, even smaller in other reaction properties [e.g. angular distributions, P(v') or P(v', J') energy distributions].