Abstract
The crystal structure of U 4Ni 11Ga 20 was derived from single crystal counter data. It has a monoclinic symmetry with space group C2/m, Z = 2, and the lattice parameters a = 2.0734(4), b = 0.4119(1), c = 1.5338(4) and β = 124.71(1)°. For a total number of 1494 independent reflections ( | F 0 | > 3 σ) using anisotropic thermal factors and weights according to the counting statistics w i = 1 (σ(F i)) 2 , the obtained reliability factor was R w = ∑| ΔF|/∑| F 0| = 0.056. The crystal structure of U 4Ni 11Ga 20 is an occupation variant of the Ho 4Ni 10Ga 21-type of structure with nickel-atoms replacing the gallium atoms in the 2d-sites at the centerpoints of distorted icosahedra. From X-ray powder diffraction analysis the compounds U 4Pd 11Ga 20 and U 4Pt 11Ga 20 were found to be isotypic with U 4Ni 11Ga 20, and practically no homogeneous region was revealed for U 4Ni, Pd, Pt 11Ga 20 at 600°C. The crystal chemistry of the new phases is discussed.
Published Version
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