Electronic Structures of NH, NH2, and NH3

Abstract

LCAO MOs have been calculated for the ground states of NH, NH2, and NH3 at various bond angles, using the LCAO—SCF method. Interactions between all electrons have been considered, but the orthogonality relationship between the 1s orbitals of nitrogen and hydrogen has been assumed. The MOs and the orbital energies disclose strong parallelisms between the a1 and the σ sets and between the b2 and the e sets, but the s-p hybridization increases with the number of hydrogen atoms. The MOs have also been investigated by a unitary transformation to the localized symmetry orbitals, and the binding energies of orbitals have been compared with Walsh's MO energy diagram. The dipole moments evaluated without configuration interaction have been discussed in comparison with the contributions of lone-pair electrons. Lower electronic states have also been calculated using the same MOs. The results obtained are in relatively good agreement with observations, but the first excited state of NH3 cannot conclusively be determined because of the disregard of the 3s orbital of nitrogen.