Theoretical kinetics investigations of the reaction HO + SO ↔ H + SO2 on an accurate full-dimensional potential energy surface

Abstract

The reaction HO + SO → H + SO₂ (R_t) and its reverse (R_-t) play an important role in environment and the combustion of sulfur-containing fuels. However, their kinetics is of high uncertainty as its reaction profile is complicated with multiple deep complexes and channels. In this work, the kinetics and mechanisms of R_t and R_-t are studied comprehensively based on a newly developed full-dimensional accurate potential energy surface (PES) with the aid of machine learning. This highly accurate PES is interfaced with the software Gaussian. Then reliable information, including the energy, structures, and vibrational frequencies of the stationary points, as well as the minimum energy path and variational analysis can be efficiently determined. The variational transition state theory (VTST) and Rice−Ramsperger−Kassel−Marcus (RRKM) theory are employed to obtain the rate coefficients of each elementary reaction. The temperature- and pressure-dependent rate coefficients of R_t are derived by the RRKM-based master equation with hindered rotor and free rotor model considered. In addition, the effect of isotope substitution for the hydrogen is investigated on the reaction kinetics. Meanwhile, the quasi-classical trajectory (QCT) calculation is performed on the PES-2020 to obtain the temperature-dependent reaction kinetics.