Zur Kristallstruktur von Ni4Nb2O9

Crystal Structure of Ni₄Nb₂O₉ Single crystals of Ni₄Nb₂O₉ were prepared and examined by X-ray work (space group C–Fd2d; a = 10.101(13), b = 17.5126(51), c = 28.6364(87) Å; Z = 32). Ni₄Nb₂O₉ has 480 atoms per unit cell, thus forming a complicated threedimensional NiO₆-octahedra framework. NbO₆-double octahedra are deposited in this framework. The relations to other A₄B₂O₉ compounds are discussed.     

Die Kristallstruktur von LiEu3O4

The crystal structure of LiEu₃O₄ which represents a new structure type was solved by usual methods with the aid of integrated WEISSENBERG photographs (MoK_α radiation, 787 reflexions) and refined to a reliability index of 4.3%. In LiEu₃O₄ just as in the first known europium(II, III)-oxide, Eu₃O₄, a clear distinction is possible between the divalent and trivalent europium ions. The given assignment which is based on crystal chemical arguments has been verified indirectly by means of the isostructural compound LiSr₂EuO₄, the cation distribution of which was established experimentally. The structure of LiEu₃O₄ is discussed in connection with the related oxides EuO and Eu₃O₄. The geometrical relations to the latter are of special interest, as LiEu₃O₄ undergoes a topotactical transformation into Eu₃O₄ by heating it in a high vacuum. There is an astonishing close structural relationship between LiEu₃O₄ and Yb₃S₄: except for lithium all the atoms are correlated as for isostructural compounds.     

Darstellung und Kristallstruktur von Rb4Br2O und Rb6Br4O

Syntheses and Crystal Structures of Rb₄Br₂O and Rb₆Br₄O In the quasi‐binary system RbBr/Rb₂O, the addition compounds Rb₄Br₂O and Rb₆Br₄O are obtained by solid state reaction of the boundary components RbBr and Rb₂O. Crystals of red‐orange Rb₄Br₂O as well as of orange Rb₆Br₄O decompose immediately when exposed to air. Rb₄Br₂O (Pearson code tI14, I4/mmm, a = 544.4(6) pm, c = 1725(2) pm, Z = 2, 175 symmetry independent reflections with I_o > 2σ(I), R₁= 0.0618) crystallizes in the anti K₂NiF₄ structure type; Rb₆Br₄O (Pearson code hR22, R3c, a = 1307.8(3) pm, c = 1646.6(5) pm, Z = 6, 630 symmetry independent reflections with I_o > 2σ(I), R₁ = 0.0759) in the anti K₄CdCl₆ structure type. Both structures contain characteristic ORb₆‐octahedra and can be understood as expanded perovskites, following the general systematics of alkaline metal oxide halides.     

Verfeinerung der Kristallstruktur von K2O2

Refinement of the Crystal Structure of K₂O₂ The crystal structure of K₂O₂ has been refined using 241 diffractometer data (Cmca; a = 6.733(1), b = 6.996(1), c = 6.474(1) Å; Z = 4; R_w = 0.050). The distance O? O (1.541(6) Å) is significantly larger than that one assumed for alkali metal peroxides, so far.     

Zur Kenntnis von Polymetaarseniten Darstellung und Kristallstruktur von BaAs2O4 · H2O

Concerning Polymetaarsenites. Preparation and Crystal Structure of BaAs₂O₄. H₂O BaAs₂O₄·H₂O was prepared by hydrothermal reaction of BaO with As₂O₃ at a temperatur of 200°C. An X-ray structural analysis demonstrated that the phase contains polymetaarsenite anions [As₄O₈^4?]_n, which adopt vierer single chains in the lattice. The relationship between the conformation of metaarsenite chains and cation size is discussed.     

Zur Kristallstruktur von CuInMo2O8

On the Crystal Structure of CuInMo₂O₈ . Single crystals of CuInMo₂O₈ were prepared and investigated by X-ray work. It shows monoclinic symmetry, space group C—C2/c; a = 9.549 Å, b = 11.529 Å, c = 5.000 Å; β = 91.38(2)°, Z = 4. CuInMo₂O₈ represents a LiYbW₂O₈ related structure, characterised by zigzag-chains of MoO₆-octahedrons and octahedrons around copper and indium. With respect to LiFeW₂O₈ the single and three-valent ions are in opposite distribution. There are strong evidence for molybdenum in lowered oxidation state.     

Die Kristallstruktur von Bi2O2Se

Bi₂O₂Se crystallizes in the (Na_0.25Bi_0.75)₂O₂Cl type structure (space group I4mmm–D _4h ¹⁷ ;a=3.891 Å,c=12.21₃ Å). The crystal chemical properties of the bismuth oxiselenide are discussed in connection with the other compounds having this structure type.

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Herrn Prof. Dr.F. Hecht zum 70. Geburtstag gewidmet.     

Die Kristallstruktur von α-CaCr2O4

The Crystal Structure of α-CaCr₂O₄ Single crystals of the high temperature modifikation α-CaCr₂O₄ were investigated by X-Ray goniometer data. (a = 11.059, b = 5.836, c = 5.114 Å, space group D–Pmmn). α-CaCr₂O₄ is isotypic with SrCr₂O₄.     

Verfeinerung der Kristallstruktur von Te2O3(SO4)

The crystal structure of ditellurium(IV)-trioxide sulfate, Te₂O₃(SO₄)—space group Pmn2₁–C _2v ⁷ ;a=8.879 (2),b=6.936 (2),c=4.646 (4) Å,Z=2—has been determined and refined by least-squares, using three-dimensionalX-ray data (1188 independent reflexions) to a final R-value of 6.3%.The crystal structure comprises puckered tellurium(IV)—oxygen layers in which the tellurium atoms are linked together by three oxygen bridges (Te–O 1.907, 1.945, 2.011 Å). The SO₄ groups are arranged between these layers. Two oxygen atoms of each SO₄ group are bonded to two adjacent tellurium atoms of one layer [Te–O(S) 2.270 Å] and the tellurium atoms show a (3+1) coordination. A third oxygen atom of the SO₄ group is in weak interaction with two adjacent tellurium atoms of the same layer (Te–O 2.603 Å) whereas the fourth oxygen atom has distances of 2.866 Å to two adjacent tellurium atoms of the next layer and effects a very weak interaction between the

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Herrn Prof. Dr.R. Kieffer zu seinem 70. Geburtstag gewidmet.     

Zur Kristallstruktur von α-TlSmW2O8

Single crystals of -TlSm(WO₄)₂ were examined by X-ray diffractometer technique (space group C _2h ⁶ -C2/c;a=10.770,b=10.597,c=7.597 Å, =130.09°,Z=4). The coordination of W⁶⁺, Sm³⁺ and Tl⁺ are discribed and discussed.-TlSm(WO₄)₂ is isotypic to -KY(WO₄)₂.

     

Die Kristallstruktur von Ca2As2O7

The structure of Ca₂As₂O₇ (a ₀=7.05,b ₀=9.30,c ₀=4.89 Å; =101.3°; space groupC2/m-C _2h ³ ;Z=2) has been solved from 465 independent X-ray intensities collected on aWeissenberg-type diffractometer up to anR-factor of 2.4% for all intensities. The structure of Ca₂As₂O₇ represents a further Thortveitite structure type.

     

Darstellung und Kristallstruktur von Ag2O3

Preparation and Crystal Structure of Ag₂O₃ The novel compound Ag₂O₃ was obtained by anodic oxidation of aqueous solutions of AgBF₄, AgClO₄, and AgPF₆. According to single crystal investigations Ag₂O₃ belongs to the orthorhombic crystal system (Fdd2; a = 1286.9(1), b = 1049.0(1), c = 366.38(5) pm; Z = 8; 309 independent diffractometer data; R = 1.2%). Ag₂O₃ is isostructural to Au₂O₃ and contains silver square-planarly coordinated by oxygen. The AgO₄ groups are connected via common vertices forming a 3-d framework.     

Zur Darstellung und Kristallstruktur von Tl2O

The preparation of Tl₂O and its crystal structure is discussed. By FOURIER methods for a monoclinic unit cell(a_M = 6.08₂, b_M = 3.52₀, c_M = 13.2₄ Å, β = 108.2°, Z = 4, space group C_2h³) the determined atomic parameters can be transformed into the trigonal system by the assumption of special oxygen positions (space group No. 166–R3 m). Correspondingly the Tl₂O crystal structure may be described as a threefold polytype form of the anti CdJ₂ type (a_H = 3,51₆ c_H = 37.8₄ Å; c/a = 10.76, Z = 6, mol. vol. = 40.7 cm³; d_x = 10.44, d_pyk = 10.4 g m^?).     

Zur Kristallstruktur von Ca2PbO4

On the Crystal Structure of Ca₂PbO₄ Single crystals of Ca₂PbO₄ were prepared by flux technique and investigated by X-ray methods. It crystallizes with orthorhombic symmetry, space group D-Pbam. (a = 5.832; b = 9.766; c = 3.375 Å, Z = 2.) Ca₂PbO₄ belongs to the Sr₂PbO₄ type. It shows Ca²⁺ in a seven fold and Pb⁴⁺ in octahedral coordination.     

Kristallstruktur von wasserfreiem Na2HPO4

Crystal Structure of Anhydrous Na₂HPO₄ Na₂HPO₄ crystallizes monoclinic in P2₁/m? C with: a = 545.(1), b = 684.7(2); c = 547.3(1) pm; β = 116.34(1)°; Z = 2. The structure consists of a nearly hexagonal close-packed arrangement of HPO₄^2? anions with Na⁺ in the “octahedral” and “tetrahedral” holes. The anions are orientationally disordered. Structural relationships with Na₂SO₄(III) and the glaserite-type of structure are discussed.