Braicovich L., Ciccacci F., Puppin E., Svane A., Gunnarsson O.
We present inverse photoemission (IP) results from FexO taken in the isochromat mode at a variety of photon energies in the ultraviolet (11.5-23-eV) and the FeO partial and total density of states calculated in the self-interaction-corrected-local-spin-density approximation (SIC-LSD). The measurements show the Fe 3d contribution just above the bottom of the conduction band E(c) and point out a contribution of the type d8L (L denotes ligand hole) 12 eV above E(c); this is superimposed on oxygen (p)-derived states. The comparison with IP and with available direct photoemission results shows the advantages of SIC-LSD over LSD: in particular, the calculations give a gap and account for a distribution of the Fe 3d character in a wide energy range (15 eV) in the ground state. Moreover, the comparison with the experiment reshows that SIC-LSD gives a satisfactory approximate evaluation of the Coulomb energy U and of the charge-transfer energy DELTA to be used in an impurity model to treat the spectral features that cannot be described by the SIC-LSD eigenvalues (d6L and d8L final states in direct and inverse photoemission, respectively).
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