The nature of the bonds in the iron silicide, FeSi, and related crystals

The iron silicide FeSi has been reinvestigated by X-ray photography of single crystals, and the reported structure for the substance has been verified. The space group is T4–P213, with a0 = 4.489 ± 0.005 A. Four iron atoms and four silicon atoms are in positions (x, x, x; x + {{1}{2}}, {{1}{2}} − x, x; ), with xFe = 0.1370 ± 0.0020 and xSi = 0.842 ± 0.004. A detailed discussion of the structure and the values of the interatomic distances has been given, by application of the resonating-valence-bond theory, and it has been shown that the interatomic distances are compatible with those found for elementary iron and elementary silicon.