Kinetic and dynamic studies of the Cl(2Pu) + H2O($\tilde X$X̃1A1) → HCl($\tilde X$X̃1Σ+) + OH($\tilde X$X̃2Π) reaction on an ab initio based full-dimensional global potential energy surface of the ground electronic state of ClH2O

Abstract

Extensive high-level ab initio calculations were performed on the ground electronic state of ClH2O. The barrier region for the title reaction was found to have significant multi-reference character, thus favoring the multi-reference configuration interaction (MRCI) method over single-reference methods such as coupled-cluster. A full-dimensional global potential energy surface was developed by fitting about 25 000 MRCI points using the permutation invariant polynomial method. The reaction path features a "late" barrier flanked by deep pre- and post-barrier wells. Calculated rate constants for the forward reaction are in reasonable agreement with experiment, suggesting a good representation of the forward barrier. The dynamics of the forward reaction was also investigated using a quasi-classical trajectory method at energies just above the barrier. While the OH bond is found to be a spectator, the HCl product has significant rotational excitation. The reaction proceeds via both direct rebound and stripping mechanisms, leading to backward and sideways scattering.