A high‐pressure study of ɛ‐FeSi, between 0 and 8.5 GPa, by time‐of‐flight neutron powder diffraction

The crystal structure of cubic iron monosilicide, ɛ‐FeSi, has been determined at six pressures between 0 and 8.5 GPa by time‐of‐flight neutron powder diffraction, using the POLARIS diffractometer at the ISIS spallation neutron source. At all pressures, the material has space group P 2 1 3, with Z = 4 and both atoms on sites 4( a ) ( x, x, x ). The unusual sevenfold coordination of both atoms is unaltered by pressure, with the atomic coordinates remaining essentially fixed at x Fe = 0.137 (1) and x Si = −0.157 (1) throughout. An almost uniform compression of up to approximately 2% in interatomic distances is observed, owing to the reduction in cell parameter.