A global ab initio potential energy surface for HNO (a3A) and quantum mechanical studies of vibrational states and reaction dynamics

A new global potential energy surface for the lowest triplet electronic state (a(3)A '') of HNO has been developed by a three-dimensional cubic spline interpolation of more than 13 000 ab initio points, which were calculated at the multireference configuration interaction level with Davidson correction using the augmented correlation-consistent polarized valence quintuple zeta basis set. Two minima and five saddle points were found on the potential energy surface. Low-lying vibrational states were obtained in this new potential using the Lanczos method and assigned. In addition, thermal rate constants for the N + OH -> H + NO reactions were obtained using an exact wave packet method. Reasonably good agreement with experimental data was obtained. (C) 2011 American Institute of Physics. [doi:10.1063/1.3592375]