HIGH-PRESSURE IN-SITU INVESTIGATION OF CUBANITE (CUFE2S3) - ELECTRONIC-STRUCTURE

An in situ study of cubanite (CuFe2S3) was performed using energy disp ersive X-ray diffraction and Mossbauer spectroscopy in a diamond anvil cell at room temperature and pressures up to 5 GPa. Mossbauer spectra of orthorhombic cubanite show a single iron site with a hyperfine mag netic field that is relatively insentive to pressure, and a centre shi ft which decreases with pressure at a rate consistent with no signific ant changes in bonding. Above 3 GPa, however, a nonmagnetic component appears that can be fitted to a single asymmetric quadrupole doublet w ith a centre shift corresponding to valence between Fe2+ and Fe3+. Thi s is consistent with X-ray diffraction data that show an accompanying transition from the orthorhombic structure to the NiAs structure, wher e localised electron transfer could occur across pairs of face-shared octahedra or extended electron delocalisation could occur along sheets of face- and edge-shared octahedra.