Ab initio surface hopping molecular dynamics on the dissociative recombination of CH3+

Abstract

Ab initio molecular dynamics (AIMD) simulations were carried out to investigate dynamics in the dissociative recombination of CH3+ at the state-averaged complete active space self-consistent field (SA-CASSCF) level. Nonadiabatic transitions between adiabatic electronic states were taken into account by the Tully's fewest switches algorithm. The direct process was examined by trajectories starting from the crossing points of the potential energy surfaces of the CH3+ ground state and CH3 dissociative state, while the indirect process was investigated by trajectories starting from the approximate crossing points of the CH3 Rydberg state and dissociative states. It is shown that, in the direct process, the dominant products, CH2 + H, are generated in 96% of trajectories, while in the indirect process, the ratio of the other products, CH + 2H, CH + H2, C + H2 + H, increases extensively due to the intramolecular energy redistribution while descending through multiple potential energy surfaces, which is more consistent with the experimental observation.