Ab initio direct dynamics studies on the reactions of H atoms with CH₃Cl and CH₃Br

A study was conducted on the title reactions by using the ab initio direct dynamics method. For each individual reaction, the theoretical rate constants in the temperature range 200-3000 K were calculated by a full improved canonical variational transition state theory plus multidimensional semiclassical tunneling correction with the potential energies information calculated directly from a combination of PMP4 and BH&H-LYP methods. It was found that the total rate constants, which were calculated from the sum of the individual rate constants, were in good agreement with experimental ones presented.