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A VO 2 single-crystal has been subject of a combined investigation by high resolution x-ray photoelectron spectroscopy (XPS), x-ray emission spectroscopy (XES) with both electron and energy-selective x-ray excitation (VLα-, VKβ 5 -and OKα-emission) and x-ray absorption spectroscopy (XAS) (O1s). We performed first principles tight-binding LMTO band structure calculations of VO 2 in both monoclinic and tetragonal rutile structures and compare the densities of states (DOS) with the experimental data. From this we conclude that the electronic structure of VO 2 is more bandlike than correlated.

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An experimental study of the electronic structure of copper intercalated titanium dichalcogenides in a wide range of copper concentrations (x = 0.04-0.8) using x-ray photoelectron spectroscopy, resonant photoelectron spectroscopy, and x-ray absorption spectroscopy has been performed. Shift towards low energies of the Ti 2p and Se 3d core level spectra and a corresponding decrease in the photon energy of Ti 2p absorption spectra with the increase in copper concentration have been found. These sign-anomalous shifts may be explained by the shielding effect of the corresponding atomic shells as a result of the dynamic charge transfer during the formation of a covalent chemical bond between the copper atoms and the TiSe2 matrix.

The results of ab initio band-structure calculations and measurements of x-ray-emission valence spectra ͑XES͒ ͑Cu L␣, V K␤ 5 , V L␣, S K␤ 1,3 , S L 2,3 ) and x-ray-photoelectron valence-band and core-level spectra ͑XPS͒ of CuV 2 S 4 thiospinel are presented. It is found that a peak in valence-conduction bands close to Fermi level is formed by V 3d states, which provide the metallic properties of CuV 2 S 4 . The valence band is formed by Cu 3d, V 3d, V 4p, and S 3p states. Examination of the XES and XPS results and the calculated charge-density maps and densities of states indicates that the valences of both Cu and V are similar to those of their elemental solids. Calculations show a strong electron-phonon coupling in CuV 2 S 4 and the prospect of superconducting behavior has not been confirmed.