Theoretical studies on the kinetics and mechanism of the reaction of atomic hydrogen with carbon dioxide

The potential energy surface for the reaction of hydrogen atom with carbon dioxide is explored by using various quantum chemical methods including W1BD, CBS-QB3, G4, G3B3, CCSD(T), QCISD(T), CCSD, M06-2X, and BB1K.Transition state theory and a modified strong collision/RRKM model are employed to calculate the thermal rate coefficients for the reaction. The results of calculation show that the overall rate constant for the reaction H + CO₂ are pressure-independent over the temperature range of 300 to 3500 K. By using the energies at the W1BD level, the non-Arrhenius expression k = 9.8T ^2.9exp(?74.8 kJ/mol/RT) L mol^?1 s^?1 was found for the reaction.