Dual-level direct dynamics calculations of the reaction rates for a Jahn-Teller reaction:: Hydrogen abstraction from CH4 or CD4 by O(3P)

We report calculations of the reaction rates of O((3)P) + CH(4) --> OH + CH(3) and O((3)P) + CD(4) --> OD + CD(3) over the temperature range 300-2500 K. The calculations are based on variational transition state theory in curvilinear coordinates with transmission coefficients calculated by the microcanonical optimized multidimensional tunneling approximation. A dual-level algorithm is used for the dynamical calculations. The higher level is UMP2/cc-pVTZ, and two lower levels are employed: PM3-SRP and an analytical potential energy surface. Using the canonical unified statistical model with microcanonical optimized multidimensional tunneling contributions, we obtain good agreement with experimental rate constants.