THE POTENTIAL-ENERGY SURFACES AND DIPOLE-MOMENT FUNCTIONS OF NH2 BY AB-INITIO EFFECTIVE VALENCE SHELL HAMILTONIAN

The second order effective valence shell Hamiltonian (H-nu), which is based on quasidegenerate many-body perturbation theory, is applied to determining the potential energy surfaces and the dipole moment functi ons of the various valence states of NH2. The H-nu calculated values a re found to be in good agreement with those of other ab initio calcula tions or experiments. It signifies the fact that the H-nu is a good ab initio method to describe the energies and properties of various vale nce states with a same chemical accuracy. Furthermore, it is shown tha t the lowest (second order for energy and the first order for property ) order H-nu method is very accurate for small molecules like NH2 and the matrix elements of H-nu which are computed only once are all we ne ed to accurately describe all the valence states simultaneously.