An accurate full-dimensional potential energy surface and quasiclassical trajectory dynamics of the H + H2O2 two-channel reaction

Abstract

We report a new full-dimensional potential energy surface (PES) of the H + H₂O₂ reaction, covering both H₂ + HO₂ and OH + H₂O product channels. The PES was constructed using the recently proposed fundamental invariant neural network (FI-NN) approach based on roughly 110 000 ab initio energy points by high level UCCSD(T)-F12/aug-cc-pVTZ calculations. The small fitting error (5.7 meV) and various tests imply a faithful representation of the discrete ab initio data over a large configuration space. Extensive quasiclassical trajectory (QCT) calculations were carried out on the new PES at a collision energy (E_c) of 15.0 kcal mol⁻¹. The reaction yields dominantly OH + H₂O, because of the lower reaction barrier and much larger reaction exothermicity (∼71 kcal mol⁻¹) for this channel. Due to the exit barrier of both reaction channels, the most available energy is partitioned into the translational motion of the products. Considerable vibrational excitations of the H₂O product are seen, particularly for the symmetric stretching and bending modes. The angular distributions show predominantly backward scattering, which is consistent with the direct rebound mechanism.