No abstract

Results of measurements of sulphur x-ray emission spectra of CuS and , excited by synchrotron radiation near the sulphur 2p threshold, are presented. An excitation energy dependence of the sulphur XES is only observed for CuS, and is attributed to the presence of inequivalent sulphur atoms in CuS. Two thirds of the sulphur atoms form dimers (as in ) while the remaining ones are single (as in ). This conclusion is confirmed by XPS measurements and LMTO band structure calculations for CuS, and . It is shown that selective excitation of x-ray emission valence spectra can be used to determine the atom-decomposed partial density of states for inequivalent sites in solids, occupied by chemically identical species.

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.

No abstract

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.