Experimental and theoretical investigation of the electronic structure of transition metal sulphides: CuS, FeS2 and FeCuS2

Abstract

Results of measurements of sulphur L-2,L-3 x-ray emission spectra of CuS and FeS2, excited by synchrotron radiation near the sulphur 2p threshold, are presented. An excitation energy dependence of the sulphur L-2,L-3 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 S-2 dimers (as in FeS2) while the remaining ones are single (as in CuFeS2). This conclusion is confirmed by XPS measurements and LMTO band structure calculations for CuS, FeS2 and CuFeS2. 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.