An ab initio potential energy surface of the reaction

A highly accurate potential energy surface (PES) for the ground state ( 1 2 A ′ ) of the title reaction has been computed using an ab initio multireference configuration interaction method (MRCI) with Davidson correction and a large orbital basis set (aug-cc-pv5z). The many-body expansion and neural network method have been used to fit a set of 10 190 ab initio points. The new potential energy surface has a root-mean-square (rms) error of 0.095 kcal/mol. The total integral reaction cross-sections have been calculated as functions of the collision energy in the range of 0–2.0 eV by means of the quasi-classical trajectory calculation (QCT).