High-pressure in situ investigation of cubanite (CuFe₂S₃): Electronic structure

Abstract

An in situ study of cubanite (CuFe₂S₃) was performed using energy dispersive X-ray diffraction and Mössbauer spectroscopy in a diamond anvil cell at room temperature and pressures up to 5 GPa. Mössbauer spectra of orthorhombic cubanite show a single iron site with a hyperfine magnetic field that is relatively insentive to pressure, and a centre shift which decreases with pressure at a rate consistent with no significant changes in bonding. Above 3 GPa, however, a nonmagnetic component appears that can be fitted to a single asymmetric quadrupole doublet with a centre shift corresponding to valence between Fe²⁺ and Fe³⁺. This is consistent with X-ray diffraction data that show an accompanying transition from the orthorhombic structure to the NiAs structure, where 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.