The crystal structure of BiNi: a complex superstructure of the InNi2 structure type

Chemical transport reactions using bromine or iodine yielded crystals of Bi Ni with a largely ordered distribution of nickel atoms on octahedral and tr igonal bipyramidal interstices within the hexagonal packing of bismuth atom s. The observed superstructure of the NiAs or InNi2 structure types is desc ribed in the monoclinic space group F1 2/m 1 (No. 12) with lattice paramete rs a = 1412.4(1), b = 816.21(6), c = 2142.9(2) pm, and beta = 90 degrees. T he pseudo-orthorhombic cell facilitates twinning along [100]. Some crystals show an additional threefold twinning along [001]. The phase width of BiNi ranges from the nickel poor to the nickel rich region. In the vicinity of the stoichiometric composition BiNi, this has only an effect on the occupat ion of a single nickel position in the crystal structure.