DUAL-LEVEL DIRECT DYNAMICS CALCULATIONS OF THE REACTION-RATES FOR A JAHN-TELLER REACTION - HYDROGEN ABSTRACTION FROM CH4 OR CD4 BY O(P-3)

We report calculations of the reaction rates of O(P-3) + CH4 --> OH CH3 and O(P-3) + CD4 --> OD + CD3 over the temperature range 300-2500 K. The calculations are based on variational transition state theory i n curvilinear coordinates with transmission coefficients calculated by the microcanonical optimized multidimensional tunneling approximation . A dual-level algorithm is used for the dynamical calculations. The h igher level is UMP2/cc-pVTZ, and two lower levels are employed: PM3-SR P and an analytical potential energy surface. Using the canonical unif ied statistical model with microcanonical optimized multidimensional t unneling contributions, we obtain good agreement with experimental rat e constants.