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The electronic structure of Al 70 Ni 15 Co 15 decagonal quasi-crystal has been studied by X-ray photoelectron spectroscopy (XPS). The disappearance of the Ni2p(3d 9 ) satellite and the decreased intensity of the 3 F state in the NiL 3 M 45 M 45 Auger spectra indicate a strong d—sp hybridization accompanied by the filling of the Ni3d bands. The filling of the Ni3d bands produces closed-shell type XPS spectra of the Ni core lines, while Co core line XPS spectra show that a significant amount of d holes are still localized on Co. This picture suggests that the magnetic properties are mainly determined by Co. The dispersion of the 3d holes is also responsible for the drop of the 3d states near E F but the angle integrated density of states does not exhibit a pseudo-gap. Finally, the correlation energy, U A , has been calculated from the kinetic energy of the 1 G term of the NiL 3 M 45 M 45 Auger emission.

A new impurity-cluster configuration-interaction model that treats charge transfer and exchange correlations on the same footing is applied to interpret the 3s core-level X-ray photoelectron spectra of NiO, CoO, K 2 NiF 4 and K 2 CoF 4 . The interplay between charge transfer and exchange correlations in determing the final state satellite structures is clarified and an estimate of the exchange integrals between the 3s hole and the 3d electrons is given. The results are consistent with the electronegativity scale, as regards charge transfer energy, and with the trend suggested by the Van Vleck rule, as concerns the exchange integrals.

Cluster model wavefunctions for the alkaline-earth oxides are analyzed to determine the origin of the trend of the chemical shifts of the binding energies, BEs, of the metal core levels. Two cancelling initial states mechanisms in the oxides are responsible for the trend. One is the increase of the BEs for the dication over the neutral atom. The second is the decrease of the free dication BEs due to the Madelung potential of the ionic oxides. The trend given by the sum of these two contributions to the chemical shifts is in full agreement with experiment. These mechanisms are electrostatic and do not involve chemical bonding effects.