I8As21Ge25

Single crystals of octaiodine henacosarsenic pentacosagermanium were grown by chemical transport reactions. The structure is isotypic with the analogous clathrates-I. In this structure, the statistically occupied clathrand atoms (As,Ge)46 form bonds in a distorted tetra­hedral coordination and their arrangement can define two polyhedra of different sizes; one is an (As,Ge)20 penta­gonal dodeca­hedron, and the other is an (As,Ge)24 tetra­kaideca­hedron. The guest atom (iodine) resides inside these polyhedra with site symmetry m3 (Wyckoff position 2a) and 2m (Wyckoff position 6d), respectively

I8Sb10Ge36

Single crystals of the title compound, octa­iodide deca­anti­monate hexa­tria­conta­germanide, were grown by chemical transport reactions. The structure is isotypic with the analogous clathrates-I. In this structure, the (Ge,Sb)46 framework consists of statistically occupied Ge and Sb sites that atoms form bonds in a distorted tetra­hedral arrangement. They form polyhedra that are covalently bonded to each other by shared faces. There are two polyhedra of different sizes, viz. a (Ge,Sb)20 dodeca­hedron and a (Ge,Sb)24 tetra­cosa­hedron in a 1:3 ratio. The guest atom (iodine) resides inside these polyhedra with symmetry m3 (Wyckoff position 2a) and 2m (Wyckoff position 2d), respectively

Redetermination of Hg2I2

The crystal structure of mercurous iodide, Hg2I2, has been determined previously from X-ray powder diffraction data [Havighurst (1926). J. Am. Chem. Soc. 48, 2113–2125]. The results of the current redetermination based on single-crystal X-ray diffraction data provide more precise geometrical data and also anisotropic displacement parameters for the Hg and I atoms, which are both situated on positions with site-symmetry 4mm. The structure consists of linear dimers I—Hg—Hg—I extending along the c axis with an Hg—Hg distance of 2.5903 (13) Å. The overall coordination sphere of the Hg+ atom is a considerably distorted octahedron. The crystal specimen under investigation was twinned by non-merohedry with a refined twin domain fraction of 0.853 (14):0.147 (14)

Cd4As2Br3

Single crystals of Cd4As2Br3 (tetracadmium biarsenide tribromide) were grown by a chemical transport reaction. The structure is isotypic with the members of the cadmium and mercury pnictidohalides family with general formula M4A2X3 (M = Cd, Hg; A = P, As, Sb; X = Cl, Br, I) and contains two independent As atoms on special positions with site symmetry -3 and two independent Cd atoms, of which one is on a special position with site symmetry -3. The Cd4As2Br3 structure consists of AsCd4 tetrahedra sharing vertices with isolated As2Cd6 octahedra that contain As–As dumbbells in the centre of the octahedron. The Br atoms are located in the voids of this three-dimensional arrangement and bridge the different polyhedra through Cd...Br contacts

Structure cristalline du composé intermétallique Ni18Ge12.

National audienc

Structure cristalline du composé Hg3-x Sb x (S+Se)2+x I2-x (x ≃ 0.1)

International audienceSingle crystals of the mercury chalcohalide Hg3-x Sb x (S+Se)2+x I2-x (x ≃ 0.1) (mercury anti-mony sulfide selenide iodide), were grown by a chemical transport reaction. The structure contains three independent A (Hg/Sb) atoms; each atom is strongly covalently bonded with two X (Se/S) atoms to form approximately linear X-A-X units. The X-A-X units link to form A 4 X 4 rings, which are combined into infinite crankshaft-type bands running along the [100] direction. Four equatorial E (I/X = Se,S) atoms at relatively long distances complete the distorted octa-hedral coordination of A (Hg/Sb). The crystal under investigation was twinned by non-merohedry with a refined twin domain fraction of 0.814 (6):0.186 (6). The structure is isotypic with Hg3Se2I2 [Beck & Hedderich (2000 ▸). J. Solid State Chem. 151, 73-76], but the current determination reveals a coupled substitution, with partial replacement of Hg(+2) by Sb(+3), balanced by the equivalent substitution of I(-1) by S(-2) and Se(-2). Bond-valence calculations are consistent with this relative substitution mode