The Potential Energy Surfaces and Dipole Moment Functions of $NH_2$ by ab initio Effective Valence Shell Hamiltonian

The second order effective valence shell Hamiltonian ($H^v$), which is based on quasidegencrate many-body perturbation theory, is applied to determining the potential energy surfaces and the dipole moment functions of the various valence states of $NH_2$. The $H^v$ calculated values are found to be in good agreement with those of other ab initio calculations or experiments. It signifies the fact that the $H^v$ is a good ab initio method to describe the energies and properties of various valence states with a same chemical accuracy. Furthermore, it is shown that the lowest (second order for energy and the first order for property) order $H^v$ method is very accurate for small molecules like $NH_2$ and the matrix elements of Hv which are computed only once are all we need to accurately describe all the valence states simultaneously.