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

Abstract

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.