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 1/8 = [(3) over bar 122]*. The resulting space group is P (1) over bar (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)Angstrom, b = 8.322(3) Angstrom, = 10.278(3) Angstrom, alpha = 73.32(4)degrees, beta = 84.41(3)degrees, gamma = 82.71(2)degrees, V = 520.60(5) Angstrom(3). High-resolution electron microscopy images revealed a well-ordered material although macroscopic crystals are twinned. (C) 2002 Elsevier Science (USA).