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(³P) + CH₄ → OH + CH₃ and O(³P) + CD₄ → OD + CD₃ 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 multi-dimensional 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.