β-Al4.5FeSi: A Combined Synchrotron Powder Diffraction, Electron Diffraction, High-Resolution Electron Microscopy and Single-Crystal X-ray Diffraction Study of a Faulted Structure

A previous single-crystal X-ray and electron diffraction structure study [Rømming et al. (1994). Acta Cryst. B 50 , 307–312] of the heavily faulted alloy phase β-Al 4.5 FeSi has been extended by synchrotron powder data and further electron microscopy and diffraction observations. Reflections that were omitted in the single-crystal work could be included in the powder refinement, which resulted in some adjustment of cell parameters and atom coordinates. The double c axis reported by some authors is explained by periodic faults in the structure, which is described in terms of a tetragonal sub-unit. Apparent discrepancies between refinement from single-crystal and powder data are discussed briefly.