AB-INITIO POTENTIAL-ENERGY SURFACE AND INTERNAL TORSIONAL-WAGGING STATES OF HYDROXYLAMINE

The two-dimensional potential energy surface describing the interactio n of the large-amplitude torsional and wagging motions in hydroxylamin e has been determined from ab initio calculations. This surface has be en sampled by a large set of grid points from a two-dimensional config uration space spanned by the torsional and wagging coordinates. At eac h grid point, the geometry optimization has been performed using the s econd-order Moller-Plesset perturbation theory with the basis set 6-31 1 + G(2d, p). At the optimized geometry, the single-point calculation of the electronic energy has been carried out using a larger basis set 6-311 + G(3df, 2p). This method was verified to yield the results com parable to those obtained by a direct optimization of the geometry wit h the basis set 6-311 + G(3df, 2p) which had been used by A. Chung-Phi llips and K. A. Jebber (1995. J. Chem. Phys. 102, 7080-7087) to calcul ate the energies of only three points in the potential energy surface of hydroxylamine. The trans and cis local minima have been found on th e determined potential energy surface. The localization features of th e torsional-wagging states have been studied by solving the two-dimens ional Schrodinger equation for the coupled torsional and wagging motio ns. (C) 1997 Academic Press.