Use of X-ray absorption spectra as a "fingerprint" of the local environment in complex chalcogenides

The local environment of tin, titanium, iron, and sulfur in spinel compound s Cu2FeSn3S8 and Cu2FeTi3S8 was studied by X-ray absorption spectroscopy (X AS) at the titanium, iron, sulfur It edges, and the tin L-1-edge, As detail ed calculations of the electronic structure of these compounds are difficul t to carry out due to the large number of atoms contained in the unit cell, the XAS spectra of the spinels are compared to those of relatively simple binary sulfides like SnS2, TiS2, and FeS. Indeed, the metal environments in these binary compounds are very similar to those in the spinels, and they can be considered good model compounds allowing the interpretation of elect ronic transitions observed in the spectra of quaternary phases. In the latt er, the bottom of the conduction band is mainly formed by Sn 5s-S 3p, Sn 5p -S 3p antibonding states for the tin-based compounds and by Ti 3d(t2g)-S 3p , Ti 3d(eg)-S 3p antibonding states for the titanium-based compounds, It it shown that the local environment of iron atoms remains unchanged when subs tituting tin with titanium atoms, according to a topotactic substitution, ( C) 2000 Academic Press.