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X-ray single-crystal studies of ZrRhGa, HfRhGa, and ZrRh/sub 0.710(4)/In

: Zumdick, M.F.; Pöttgen, R.; Zaremba, V.I.; Hoffmann, R.-D.


Journal of solid state chemistry 166 (2002), Nr.2, S.305-310
ISSN: 0022-4596
Fraunhofer IFAM ()
Fraunhofer IFAMDD ()
X-ray diffraction; electron diffraction; chemical bonding

ZrRhGa, HfRhGa, and ZrRh/sub 0.710(4)/In were prepared by arc melting of the elements under an argon atmosphere and subsequent annealing. The three compounds were investigated by X-ray diffraction on powders and single crystals: ZrNiAl-type, space group P62m, a=721.4(2) pm, c=336.7(2) pm, wR2=0.0366, 191 F/sup 2/ values, 14 parameters for ZrRhGa, a=724.2(3) pm, c=328.0(1) pm, wR2=0.0326, 191 F/sup 2/ values, 14 parameters for HfRhGa, and a=0741.91(7) pm, c=335.8(1) pm, wR2=0.0339, 202 F/sup 2/ values, and 14 parameters for ZrRh/sub 0.710(4)/In. Anisotropic refinement of the Rhl positions of ZrRhGa and HfRhGa showed extremely large U/sub 33/ values. These sites have been refined with a split position 00/sub z/ (2e) instead of 000 (2a) with an occupancy of 50%. Both gallides have carefully been investigated by low- temperature X-ray data and electron diffraction. These data gave no indication for an ordering of the rhodium atoms. Structural motifs of both gallides are rhodium-centered trigonal prisms [Rh1Ga/sub 6/], [Rh2Zr/sub 6/], and [Rh2Hf/sub 6/], respectively. The prisms are condensed via common edges and faces. The Rhl position in the indide is occupied only by 12% resulting in the composition ZrRh/sub 0.710(4)/In for the investigated crystal. The geometrical restrictions and chemical bonding of these intermetallics are discussed