Study of the NH Radical by the LCAO-SCF Molecular Orbital Method

Wave functions, orbital energies, and total molecular energies have been obtained for the ground and five excited states of the NH radical. The Roothaan method was used, modified for the case of a molecule with unfilled orbitals. Separate self-consistent procedures were carried out for the ground state and a doubly excited state, while results for the intermediate excited states could be calculated with the ground state orbitals. Dissociation energies, dipole moments, and electron population analyses were also computed. Comparison with the sparse experimental data indicates that the calculated states are too widely separated in energy. It is also found that this complete treatment gives higher energy values than Higuchi reported in an incomplete computation employing various approximations, although the wave functions are little changed. In general, results seem to be about as reliable for the diatomic open shell case as for the usual closed shell molecules. Contrary to Sahni's suggestion, they do not appear to be better for the heteronuclear than for the homonuclear case.