An SCF LCAO MO Study of N2

The self-consistent-field molecular-orbital method in the LCAO (linear combination of atomic orbitals) approximation is applied to the ground-state configuration of the nitrogen molecule at the observed equilibrium internuclear separation. No other approximations are used; all electrons are included. The forms of the resulting molecular orbitals are discussed. The s-p hybridization is computed to be 26.1 percent in agreement with Mulliken's magic formula estimation of 21 percent. The quadrupole moment is computed to be —1.87 a.u. (experiment, 1.11 a.u. of undetermined sign). The ratio of the computed to the experimental total molecular energy is found to be 0.9905. Ionization potentials and single-electron excitation energies are computed and compared with experimental spectroscopic values. The spectral results are more encouraging than have been hitherto reported from calculations by the LCAO molecular-orbital method. The approximation of neglecting the inner-outer-shell mixing, as it has usually been done in computations of this type, somewhat changes the present results and is not recommended.