Electronic states and nature of bonding of the molecule NiGe by all electron ab initio Hartree–Fock (HF) and configuration interaction (CI) calculations and mass spectrometric equilibrium experiments

All electron ab initio Hartree–Fock (HF) and configuration interaction (CI) calculations have been applied to investigate the low-lying electronic states of the NiGe molecule. The ground state of the NiGe molecule is predicted to be 1Sigma+. The chemical bond in the 1Sigma+ ground state is a double bond composed of one sigma and one pi bond. The sigma bond is due to a delocalized molecular orbital formed by combining the Ni 4s and the Ge 4psigma orbitals. The pi bond is a partly delocalized valence bond, originating from the coupling of the 3dpi hole on Ni with the 4ppi electron on Ge. The low-lying electronic states of the NiGe molecule have all been characterized by the symmetry of the hole in the 3d shell of Ni. The dissociation energy of the NiGe molecule has been determined from our high temperature mass spectrometric equilibrium data in combination with the theoretical results as D ^{[open circle]} ₀ =286.8±10.9 kJ mol−1. The standard heat of formation of the NiGe molecule has been obtained as DeltaH ^{[open circle]} _f,298 =514±12 kJ mol−1. The Journal of Chemical Physics is copyrighted by The American Institute of Physics.