The crystal structure of Ni₁₀Sn₅P₃

Selected-area electron diffraction revealed that Ni₁₀Sn₅P₃ forms a superstructure of the NiAs-type structure. All observed reflections could be fully indexed as H = G + mq, where G represents the reflections of the underlying hexagonal B8-type average structure, m is an integer and q = 1/8[3̄122]*. The resulting space group is P1̄ (Z = 2). The crystal structure was refined using single-crystal X-ray diffraction methods on a twinned specimen (1651 observed unique reflection, R_{w obs} = 0.0391). The superstructure reflections are caused by ordering of Sn and P atoms on the hcp array coupled to Ni ordering in 1/4 of the trigonal bipyramidal sites. The unit-cell parameters refined from powder X-ray diffraction data are a = 6.419(2) Å, b = 8.322(3) Å, c = 10.278(3) Å, α = 73.32(4)°, β = 84.41(3)°, γ = 82.71(2)°, V = 520.60(5) ų. High-resolution electron microscopy images revealed a well-ordered material although macroscopic crystals are twinned.