Direct dynamics investigation of the reaction S(3P) + CH4 → CH3 + SH(2Π)

Geometries, frequencies, and energies of the hydrogen abstraction reaction S(3P) + CH4 were computed using DFT methods, coupled-cluster theory, various basis sets, and an extrapolation scheme to assess the complete basis set limit (CBS) energies. The M05-2X/MG3S approach gives values of the classical barrier height (28.3 kcal mol−1) and reaction energy (23.9 kcal mol−1) in good agreement with the CCSD(T)/CBSD–Q results, i.e., 30.2 and 24.7 cal mol−1, respectively. At the range of 1140–1480 K, the VTST thermal rate constants are in agreement with experiment and, in general, the ratio between experimental and the CVT/SCT values varies from 1.9 to 1.3.