Quasiclassical trajectory calculations of the HO2 + NO reaction on a global potential energy surface

We report quasiclassical trajectory calculations of the HO2 + NO reaction using a new full dimensional, singlet potential energy surface ( PES) which is a fit to more than 67 000 energies obtained with density functional theory-B3LYP/6-311G(d,p)-calculations. The PES is invariant with respect to permutation of like nuclei and describes all isomers of HOONO, HONO2, saddle points connecting them and the OH + NO2, HO2 + NO channels. Quasiclassical trajectory calculations of cross-sections for the HO2 + NO to form HOONO, HONO2 and OH + NO2 are done using this PES, for reactants in the ground vibrational state and rotational states sampled from a 300 K Boltzmann distribution. Trajectory calculations illustrate the pathway that HO2 + NO takes to the energized HOONO complex, which dissociates to products OH + NO2, reactants HO2 + NO, or isomerizes to HONO2. The association cross sections are used to obtain rate constants for formation of HOONO and HONO2 in the high-pressure limit, and formation of products OH + NO2 in the low-pressure limit.