Rigorous close-coupling quantum dynamics calculation of thermal rate constants for the water formation reaction of H2 + OH on a high-level PES.

Thermal rate constants for the prototypical H2 + OH → H + H2O reaction are calculated using quantum dynamics simulations including all degrees of freedom and accurately accounting for overall rotation via close-coupling. Results are reported for a recent, highly accurate neural network potential [J. Chen et al., J. Chem. Phys. 138, 154301 (2013)] and compared to results obtained on a previous, semi-empirical potential. Thermal rate constants between 300 K and 1000 K are reported and very good agreement with experimental work is found. Additionally, reasonable agreement for the close-coupling simulations on both potentials is found. In contrast to previous work, we find that the J-shifting approximation works well for the title reaction given that a high-level PES is used for the dynamics calculation. Moreover, the importance of treating the spin-orbit coupling in the reactant partition function is discussed. The highly accurate results reported here will provide a benchmark for the development of approximate methods.