A global H2O potential energy surface for the reaction O(1D)+H2→OH+H

A global, single-valued ground-state H2O potential surface for the reaction O(1D)+H2→OH+H has been constructed from a new set of accurate ab initio data using a general multidimensional interpolation method. The ab initio calculations are of the multireference, configuration interaction variety and were carried out using augmented polarized triple zeta basis sets. The multidimensional method is formulated within the framework of the reproducing kernel Hilbert space theory. The H2O potential is expressed as a many-body sum of a single one-body term, three two-body terms, and a single three-body term. The one-body term is the dissociation energy to the three-atom limit 2H(2S)+O(3P). The two-body terms are two O–H and one H–H adiabatic diatomic potentials of lowest energy. Each diatomic term is obtained by interpolating a discrete set of ab initio data using a one-dimensional, second-order, distancelike reproducing kernel. The three-body term is obtained by interpolating the difference of the H2O ab initio data and the one- and two-body sum by means of a direct product of three one-dimensional reproducing kernels on an optimized regular three-dimensional grid. The H2O potential energy surface is accurate, globally smooth, easy to evaluate, and asymptotically correct. Extensive quasiclassical trajectory calculations based on this new potential energy surface have been performed and compared with the results based on the potential energy surface of Murrell and Carter (MC) and that of Schinke and Lester (SL). Comparisons with recent experimental measurements on total cross sections, isotope effects, rate constants, vibrational, rotational, and angular distributions of the O(1D)+H2/HD reaction show that the new potential energy surface is a significant improvement over the MC and SL surfaces.