Electronics states of a surface nickel atom on the nickel (001) surface

Electronic states of a Ni(001) surface atom, corresponding to different d-occupations, are calculated for a 49 atom cluster model of the surface. SCF and CI calculations on a variety of low lying states are reported. Strong mixing between d⁹ and d¹⁰ configurations is found for the lowest states of different symmetries with the splitting between the states ranging from 1.7 to 2.0 eV. In contrast, the d⁸ configurations do not interact strongly with other d configurations and lie energetically much higher at 3.0 eV. Thus, the splitting between d⁹ and d¹⁰ configurations is comparable to that of the isolated atom whereas the d⁸ configuration is greatly destabilized. The cluster produces a manifold of closely spaced electronic states above the ground state thus modeling the density of unoccupied states above the Fermi level.