New Indides Sc6Co2.18In0.82, Sc10Ni9In19.44 And Sccu4In – Synthesis, Structure, And Crystal Chemistry

Abstract

New indides Sc6Co2.18In0.82, Sc10Ni9In- and ScCu4In have been synthesized from the elements by arc-melting. Single crystals were grown by special annealing modes. The thee indides were investigated via X-ray powder and single crystal diffraction: Ho6Co2Ga type, Immm, a = 886.7(3), b = 878.0(2), c = 932.1(3) pm, wR2 = 0.0517, 711 F2 values, 35 variables for Sc6Co2.18In0.82, Ho10Ni9In20 type, P4/nmm, a = 1287.5(2), c = 884.7(1) pm, wR2 = 0.0642, 1221 F2 values, 63 variables for Sc10Ni9In19.44, and MgCu4Sn type, F ¯43m, a = 704.03(7) pm, wR2 = 0.0267, 101 F2 values, and 7 variables for ScCu4In. The scandium rich indide Sc6Co2.18In0.82 contains two Co2 dumb-bells at Co-Co distances of 221 and 230 pm. Each cobalt atom within these dumb-bells has a tricapped trigonal prismatic coordination. The In1 site has a distorted cube-like coordination by scandium and shows a mixed occupancy (36%) with cobalt. The In2 atoms have distorted icosahedral scandium coordination. As a consequence of the small size of the scandium atoms, the In4 site in Sc10Ni9In19.44 shows defects and was furthermore refined with a split model leading to a new distorted variant within the family of Ho10Ni9In20 compounds. ScCu4In is an ordered version of the cubic Laves phase with scandium and indium atoms in the CN16 voids of the copper substructure. The Cu-Cu distances within the three-dimensional network of corner-sharing tetrahedra are 248.6 and 249.2 pm. The crystal chemical peculiarities of these three indide structures are briefly discussed