Direct ab initio dynamics study for the hydrogen abstraction reaction: CH₂(³B₁) + H₂CO → CH ₃ + CHO

We present a direct ab initio dynamics study of thermal rate constants of the hydrogen abstraction reaction of CH₂(³B₁) + H₂CO → CH₃ + CHO. The MP2/cc-pVDZ method is employed to optimize the geometries of stationary points as well as the points on the minimum energy path. The energies of all the points were further refined at the CCSD(T)/cc-pVTZ level of theory based on the Moller-Plesset perturbation theory (MP2) optimized geometries. The rate constants were evaluated using the conventional transition state theory, the canonical variational TST, and the improved canonical variational TST, also both including small-curvature tunneling correction in the temperature range of 300-2,500 K. The calculated results show that the rate constants have positive temperature dependence in the calculated temperature range. The calculated results show that the tunneling effect is important at low temperature region.