A new ab initio potential-energy surface for NH2(X 2A") and quantum studies of NH2 vibrational spectrum and rate constant for the N(2D)+H2-->NH+H reaction

A new global potential-energy surface for the ground electronic state of NH(2)(X (2)A(")) has been constructed by three-dimensional cubic spline interpolation of more than 20 000 ab initio points, which were calculated at the multireference configuration-interaction level with Davidson correction using the augmented correlation-consistent polarized valence quadruple-zeta basis set. The new potential is shown to yield better overall agreement with the experimental vibrational frequencies of NH(2) and its isotopomers. In addition, the rate constant for the N((2)D)+H(2)(X (1)Sigma(g) (+))-->NH(X (3)Sigma(-))+H((2)S) reaction was calculated up to 600 K and the agreement with experimental data is substantially improved over previous results.