A neural network potential energy surface and quantum dynamics studies for the Ca(S) + H → CaH + H reaction.

Reactive collisions of Ca ions with H molecules play a crucial role in ultracold chemistry, quantum information and other cutting-edge fields, and have been widely studied experimentally, but the corresponding theoretical studies have not been reported due to the lack of an applicable potential energy surface (PES). Herein, a globally accurate PES of the ground-state CaH is constructed using the permutation invariant polynomial neural network method based on 27 780 points calculated at the multi-reference configuration interaction level. On the new PES, the quantum time-dependent wave packet calculations are performed to study the dynamics mechanisms of the Ca(S) + H( = 0, = 0) → CaH + H reaction. The calculated results suggest that the reaction follows a direct abstraction process when the collision energy is below 5.0 eV. The dynamics results would have a great reference significance for the experimental research of this reactive system at a finer level, and further dynamics studies, such as the effects of isotope substitution and rovibrational excitations of the reactant molecule, could be carried out on this newly constructed PES.