Influence of the sulfur vacancies on the electronic properties of In16Sn4S32

High and low temperature forms of In,,Sn,S,, differ in color (black and ora nge-red, respectively) and lithium insertion properties. We have studied bo th forms by X-ray and neutron diffraction techniques and Sn-199 Mossbauer s pectroscopy. While diffraction techniques show no structural difference, Mo ssbauer spectra allow to differentiate both phases, as a consequence of the presence of Sn-II in the high-temperature form. We show from tight-binding calculations that both the differences in color and the tin oxidation stat es are related to the existence of sulfur vacancies in the local environmen t of the tin atoms. (C) 2001 Editions scientifiques ct medicales Elsevier S AS. All rights reserved.