Die Kristallstruktur von W2CoB2 und isotypen Phasen

Zusammenfassung Die Phasen Mo₂CoB₂, Mo₂NiB₂, W₂FeB₂, W₂CoB₂ und W₂NiB₂ kristallisieren in einem neuen Typ (W₂CoB₂-Struktur). Die Zelle ist orthorhombisch, die Raumgruppe D _2h ²⁵ -I mmm. Die Punktlagen sind 4 W in 4 f), 2 Co in 2 a) und 4 B in 4 h). Die strukturellen Bauelemente werden mit jenen von Mo₂FeB₂ (U₃Si₂-Typ) verglichen.

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The ternary compounds Mo₂CoB₂, Mo₂NiB₂, W₂FeB₂, W₂CoB₂ and W₂NiB₂ crystallize with a new type (W₂CoB₂-structure). The elementary cell is orthorhombic, the space group being D _2h ²⁵ -I mmmm. The atomic positions are determined to be 4 W in 4 f), 2 Co in 2 a) and 4 B in 4 h). Both crystal structures W₂CoB₂ and Mo₂FeB₂ (U₃Si₂-type) are compared with respect to the trigonal prismatic surrounding of the boron atoms.

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Über einige Komplexboride mit Platinmetallen

Zusammenfassung Die Kristallstrukturen von W₂Ir₃B_6–x (x1) und von Mo₂IrB₂ werden mit Hilfe von Einkristalldaten bestimmt. Mo_2,5Ir_2,5B₅ ist mit der erstgenannten Kristallart isotyp, weist aber eine mehr statistische Verteilung der Metallatome auf. In Mo₂IrB₂ liegen B₄-Gruppen vor. (Cr,Ru)B und (Cr,Os)B kristallisieren im FeB-Typ; (Mo,Ru)B ist mit CrB und (Mo,Ru)₃B₄ mit Ta₃B₄ isotyp. Die strukturchemischen Bauprinzipien binärer und ternärer Boride werden im Bereich 40–60 At% B diskutiert.

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Complex borides with platinum metals

The crystal structures of W₂Ir₃B_6–x (x1) and Mo₂IrB₂ have been derived by means of single crystal photographs. Mo_2.5Ir_2.5B₅ is isotypic with W₂Ir₃B_6–x , displays a more statistical distribution, however, of the two kind of metal atoms. In Mo₂IrB₂ there are B₄-groups present. (Cr,Ru)B as well as (Cr,Os)B crystallize with FeB-type structure, (Mo,Ru)B with CrB-type structure and (Mo,Ru)₃B₄ is isotypic with Ta₃B₄. The principles of the structural chemistry of binary and ternary borides within the range of 40–60 at. % boron will be discussed.

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Herrn Prof. Dr. Dr. E. h.Otto Kratky zum 70. Geburtstag gewidmet.     

Spinelle mit substituierten Nichtmetallteilgittern. IV. Rötgenographische Untersuchung der Systeme CuCr2(S1−xSex)4 und CuCr2(Se1−xTex)4

Spinels with substituted Nonmetal Sublattices. IV. CuCr₂(S_1?xSe_x)₄ and CuCr₂(Se_1?xTe_x)₄ Polycrystalline samples of the spinel system CuCr₂(S_1?xSe_x)₄ have been prepared with 0 ≤ x ≤ 1. We found that in the spinel system CuCr₂(Se_1?xTe_x)₄ no solid solution is existent in the range 0.01 ≤ x ≤ 0.70. When S is substituted by Se and Se by Te the lattice constants increase linearely by 0.52 Å and 0.81 Å respectively. The anion-sublattice shows random distribution of the chalcogen atoms, the chalcogen parameters u are constant in the system CuCr₂(S_1?xSe_x)₄ with a mean value of u = 0.382₉. The calculated anion-cation-distances lead to a covalent tetrahedral radius r_Cu = 1.23 Å. This radius is in agreement with the radius r_Cu = 1.22 Å of Cu spinels with Cu in the valence +1.     

Synthese und Kristallstrukturen von DyPt8P2 und Mg10−xPt9P7

Synthesis and Crystal Structures of DyPt₈P₂ and Mg_10?xPt₉P₇ Single crystals of DyPt₈P₂ (a = 9.260(2), b = 4.005(1), c = 9.633(2) Å, β = 102.64(3)°) were grown by heating the elements in a melt of NaCl/KCl at 1100 °C. The phosphide crystallizes in a new type of structure (I2/m; Z = 2) which consists of fragments in the shape of a cubic close packing built up by three fourths of the platinum atoms. The Dy atoms are coordinated by twelve Pt and four P atoms forming a distorted hexagonal prism which is fourfold capped by Pt atoms. Needles of Mg_10?xPt₉P₇ (a = 18.121(4), b = 23.316(5), c = 3.848(1) Å) were obtained by reaction of the elements in molten lead at 1000 °C. The main feature of the new type of structure (Pbam; Z = 4) is an oval ring of pentagonal prisms formed by each six Pt and four P atoms. The prisms are linked with each other via common faces and they are centered by Mg atoms. Another Mg atoms are located in holes of the three‐dimensional [Pt₉P₇] network. It is remarkable, that one of the ten different crystallographic sites of the Mg atoms is occupied incompletely inducing the composition Mg_10?xPt₉P₇ with x = 0.86.     

Spinelle mit substituierten Nichtmetallteilgittern. V. Röntgenographische Untersuchung des Spinellsystems CuRh2(S1−xSex)4

Spinels with Substituted Nonmetal Sublattices. V. X-Ray Investigation of the Spinel System CuRh₂(S_1?xSe_x)₄ Polycrystalline samples of the spinel system CuRh₂(S_1?xSe_x)₄ were prepared with 0 ≤ x ≤ 1. When S is substituted by Se the lattice constants increase linearly by 0.48 Å. The anion sublattice shows random distribution of the chalcogen atoms with a mean value for the chalcogen parameter of u = 0.381. The cation-anion distances were calculated.     

High-temperature defect structure and electrical conduction in Ni1−xMgxO

The ionic transference number, the electrical conductivity, and Seebeck coefficient of Ni_1?xMg_xO (0.1 ≤ x ≤ 0.9) were measured as functions of temperature (900–1400°C) and oxygen partial pressure (10²–10⁵ Pa). The contribution of ionic conduction to the total conductivity of Ni_0.9Mg_0.1O was of the order of 10^?3?10^?2 at 900–1300°C, which led us to assume that the electronic conduction was predominating in Ni_1?xMg_xO (x ≤ 0.9). The electrical conductivities of both undoped and Al-doped Ni_1?xMg_xO depended on the $\text{1}\text{4}$ power of P_O2, which indicated a significant impurity effect on the defect equilibria and was interpreted as showing that doubly ionized cation vacancies were the dominant point defects at high temperatures. Analyses of the difference in the temperature dependences of conductivity and Seebeck coefficient showed that band-like conduction took place in the NiO-rich composition range (x ≤ 0.1), while thermally activated hopping of small polarons occurred in Ni_1?xMg_xO with x ≥ 0.3. The calculated drift mobility abruptly decreased in the composition region where the conduction mechanism changed.     

New complex borides with ReB2- and Mo2IrB2-type structure

The compound V_0.4Os_0.6B₂ was found to crystallize with ReB₂-type structure. V₂OsB₂, Mo₂OsB₂, and W₂OsB₂ are isotypic with the crystal structure of Mo₂IrB₂. The crystal chemistry of complex borides with ReB₂- and Mo₂IrB₂-type structure is discussed.     

Etude par diffraction neutronique de la phase “Cs4−xYb12F40−x” (0 ≤ x ≤ 1): Hypothèse structurale

The structure of the phase Cs_4?xYb₁₂F_40?x(0 ≤ x ≤ 1) has been determined by a single-crystal neutron diffraction study. It has been solved in the space group P6₃mc and refined to the best R factor of 0.0535 for the formula Cs_3.4Yb₁₂F_39.4 (324 independent reflections). Three edge-sharing pentagonal bipyramids surrounding three ytterbium atoms form Yb₃F₁₆ groups and the structure is described as the superposition, according to the sequence A₁A₂B₁B₂A₁A₂…, of sheets of corner-sharing Yb₃F₁₆ groups with a possible transformation of bipyramids into octahedra in the A₂ and B₂ layers. These sheets are joined together by the axial fluorine atoms of the bipyramids or octahedra. Cesium atoms are located in the tunnels formed by their stacking. It is shown that the Cs_4?xYb₁₂F_40?x phase (0 ≤ x ≤ 1) is an intermediate step of the Cs_4?xYb₁₂F_40?x solid solution observed with 0 ≤ x ≤ 2 and corresponds to a superstructure of the high-temperature YbF₃ phase.     

Die Kristallstruktur des W3CoB3 und der dazu isotypen Phasen Mo3CoB3, Mo3NiB3 und W3NiB3

Zusammenfassung Mo₃CoB₃, Mo₃NiB₃, W₃CoB₃ und W₃NiB₃ kristallisieren in einem eigenen Typ (W₃CoB₃-Struktur). Das trigonal prismatische Bauelement [T ₆B]^* ist zu Ketten vereinigt, wobei B₃-Gruppen entstehen. Die Phasen sind vermutlich Bor-reicher als obiger Formel entspricht.

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The crystal structure of W₃CoB₃ and the isotypic phases Mo₃CoB₃, Mo₃NiB₃, and W₃NiB₃

Mo₃CoB₃, Mo₃NiB₃, W₃CoB₃, and W₃NiB₃ were found to possess a new type of crystal structure (W₃CoB₃-structure type). Trigonal prismatic groups [T ₆B]^* are linked together forming chains in such a way that B₃-groups occur. These borides do probably exist with a larger amount of boron as to compared with the formula.

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Mg2Ru5B4 und Mg5Ru13B11, zwei ternäre Magnesium-Rutheniumboride mit Kanalstrukturen

Mg₂Ru₅B₄ and Mg₅Ru₁₃B₁₁, Two Ternary Magnesium Ruthenium Borides with Channel Structures The ternary borides Mg₂Ru₅B₄ and Mg₅Ru₁₃B₁₁, crystallizing in the orthorhombic space group Pbam, were prepared by reaction of the elementary components in sealed tantalum ampoules. Mg₂Ru₅B₄ (a = 1000.0(2) pm, b = 837,6(1) pm, c = 295.42(3) pm, Z = 2, R_W = 0.027 for 563 reflections) is homeotypic with Sc₂Ru₅B₄. The structure contains BRu₆-trigonal prisms, connected by faces and edges to form pentagonal channels filled with chains of magnesium atoms. Mg₅Ru₁₃B₁₁ (a = 2190.1(2) pm, b = 996.7(2) pm, c = 294.65(3) pm, Z = 2, R_W = 0.031 for 959 reflections) has a similar but so far unknown structure in which parts of the magnesium and boron atoms are disordered.     

Stabilizing the LaCoAl4 Structure through Indium‐Magnesium Substitution in CeRhIn4−xMgx (x = 0.79 and 0.84) – An Indide with Magnesium Centered Indium Cubes

The intermetallic compounds CeRhIn_4?xMg_x (x = 0.79 and 0.84) were prepared from the elements in sealed tantalum ampoules in a high‐frequency furnace. The samples were investigated by X‐ray powder and single crystal diffraction: LaCoAl₄ type, Pmma, a = 829.5(2), b = 433.56(9), c = 740.2(2) pm, wR2 = 0.0458, 651 F² values, 25 variables for CeRhIn_3.21Mg_0.79 and a = 831.44(10), b = 433.49(10), c = 741.04(10) pm, wR2 = 0.0543, 915 F² values, 25 variables for CeRhIn_3.16Mg_0.84. The indium atoms build up two‐dimensional networks perpendicular to the b axis in an AA stacking sequence leaving slightly distorted trigonal, square and pentagonal prismatic voids for the rhodium, magnesium, and cerium atoms. Both square prismatic voids show small magnesium/indium mixing. The shortest interatomic distances occur for the Rh–Mg contacts (257 pm). Together, the rhodium, indium, and magnesium atoms build up three‐dimensional [RhIn_4?xMg_x] networks in which the cerium atoms fill distorted pentagonal channels.     

Two‐ and Three‐Dimensional [IrSi] Networks in the Silicides Sm3Ir2Si2, HoIrSi,and YbIrSi

New intermetallic rare earth iridium silicides Sm₃Ir₂Si₂, HoIrSi, and YbIrSi were synthesized by reaction of the elements in sealed tantalum tubes in a high‐frequency furnace. The compounds were investigated by X‐ray diffraction both on powders and single crystals. HoIrSi and YbIrSi crystallize in a TiNiSi type structure, space group Pnma: a = 677.1(1), b = 417.37(6), c = 745.1(1) pm, wR2 = 0.0930, 340 F² values for HoIrSi, and a = 667.2(2), b = 414.16(8), c = 742.8(2) pm, wR2 = 0.0370, 262 F² values for YbIrSi with 20 parameters for each refinement. The iridium and silicon atoms build a three‐dimensional [IrSi] network in which the holmium(ytterbium) atoms are located in distorted hexagonal channels. Short Ir–Si distances (246–256 pm in YbIrSi) are indicative for strong Ir–Si bonding. Sm₃Ir₂Si₂ crystallizes in a site occupancy variant of the W₃CoB₃ type: Cmcm, a = 409.69(2), b = 1059.32(7), c = 1327.53(8) pm, wR2 = 0.0995, 383 F² values and 27 variables. The Ir1, Ir2, and Si atoms occupy the Co, B2, and B1 positions of W₃CoB₃, leading to eight‐membered Ir₄Si₄ rings within the puckered two‐dimensional [IrSi] network. The Ir–Si distances range from 245 to 251 pm. The [IrSi] networks are separated by the samarium atoms. Chemical bonding in HoIrSi, YbIrSi, and Sm₃Ir₂Si₂ is briefly discussed.     

Novel Derivatives of the CaIn2 Type of Structure: Yb1+xMg1—xGa4 (0 ≤ x ≤ 0.058) and YLiGa4

The compounds Yb_1+xMg_1—xGa₄ (0 ≤ x ≤ 0.058) and YLiGa₄ were synthesized by direct reaction of the elements in sealed niobium crucibles. The atomic arrangement of Yb_1+xMg_1—xGa₄ (x = 0.058) represents a new structure type (space group P6¯m2, a = 4.3979(3)Å and c = 6.9671(7)Å) as evidenced by single crystal structure analysis and can be described as an ordered variant of CaIn₂. YLiGa₄ is isotypic to the ytterbium compound according to X‐ray Guinier powder data (a = 4.3168(1)Å and c = 6.8716(2)Å). Measurements of the magnetic susceptibility of both compounds reveal intrinsic diamagnetic behaviour, i.e., ytterbium in the 4f¹⁴ configuration for Yb_1+xMg_1—xGa₄ (x = 0). From electrical resistivity data both compounds can be classified as metals. The compressibility of Yb_1+xMg_1—xGa₄ (x = 0.058) as measured in diamond anvil cells by angle‐dispersive X‐ray diffraction is compatible with a valence change of the ytterbium atoms at high‐pressures and indicates a slight anisotropy which is in accordance with the structural organisation of the gallium network. X‐ray absorption spectra of the Yb L_III edge of Yb_1+xMg_1—xGa₄ (x = 0.058) at pressures up to 25.0 GPa show a two‐peak structure which reveals the presence of Yb in the 4f¹⁴ and 4f¹³ states. The amount of ytterbium in the 4f¹³ state increases in two steps with progressing compression. The bonding analysis by means of the electron localization function reveals the Zintl‐like character of both compounds and confirms the 4f¹⁴ state for the majority of ytterbium atoms.     

Solid solutions of double phosphate hexahydrates in the MgNH4PO4 · 6H2O-Ni2+-H2O system and their dehydration products

Substitutional solid solutions Mg²⁺ ? Ni²⁺ of crystal hydrates Mg_{(1 ? x)}Ni _x NH₄PO₄ · 6H₂O and Mg_{(1 ? x)}Ni _x NH₄PO₄ · H₂O (where 0 < x ≤ 0.65), which have struvite structure and dittmarite structure, respectively, have been studied. Ion exchange Mg²⁺ ? Ni²⁺ influences the condition of M²⁺-H₂O (M²⁺ = Mg²⁺, Ni²⁺) coordination bonds and hydrogen bonds involving coordinated H₂O molecules, as probed by X-ray powder diffraction, thermal analysis, and FTIR spectroscopy. The coordination of water molecules to metal ions in those crystal hydrates is treated to be a factor that determines the propensity of the resulting crystal structures to polymorphism.     

Magnetic behavior in solid solution systems: I. (MnMg)Tb2S4

The solid solutions in the system Mn_xMg_1?xTb₂S₄ for 0 ≤ x ≤ 1 all have the orthorhombic MnY₂S₄ structure, space group Cmc2₁. In the temperature range 77–300 K the materials are paramagnetic and the Curie-Weiss law is obeyed. At low temperatures, ca. 20 K, there is a deviation from linearity of the curve of χ^?1 vs T. The curves of magnetization as a function of the magnetic field at 4.2 K are reminiscent of saturation curves, especially for low values of x. The magnetic interactions between the metal ions are discussed.     

Photolumineszenz im System A2II B1/4II Gd1/2−x Eux □1/4 WO6 ≙ A8II BII Gd2−x Eux □ W4O24 (AII,BII = Sr,Ba)

Photoluminescence in the System A₂^II B_1/4^IIGd_1/2?xEu_x□_1/4WO₆ ? A₈^IIB^IIGd_2?xEu_xW₄O₂₄ (A^II, B^II = Sr, Ba) The emission and excitation spectra for the series Sr₈SrGd_2?xEu_x□W₄O₂₄ (HT- and LT-modifications) and Sr_9?yBa_yEu₂□W₄O₂₄ are reported and discussed. HT- and LT-Sr₈SrEu₂□W₄O₂₄ show an intense red emission, no concentration quenching is present.     

Phase formation in the Ag<Subscript>2</Subscript>MoO<Subscript>4</Subscript>-MgMoO<Subscript>4</Subscript>-Al<Subscript>2</Subscript>(MoO<Subscript>4</Subscript>)<Subscript>3</Subscript> system

The subsolidus region of the Ag₂MoO₄-MgMoO₄-Al₂(MoO₄)₃ ternary salt system has been studied by X-ray phase analysis. The formation of new compounds Ag_{1 ? x} Mg_{1 ? x} Al_{1 + x} (MoO₄)₃ (0 ≤ x ≤ 0.4) and AgMg₃Al(MoO₄)₅ has been determined. The Ag_{1 ? x} Mg_{1 ? x} Al_{1 + x} (MoO₄)₃ variable-composition phase is related to the NASICON type structure (space group R \(\bar 3\) c). AgMg₃Al(MoO₄)₅ is isostructural to sodium magnesium indium molybdate of the same formula unit and crystallizes in triclinic system (space group P \(\bar 1\), Z = 2) with the following unit cell parameters: a = 9.295(7) Å, b = 17.619(2) Å, c = 6.8570(7) Å, α = 87.420(9)°, β = 101.109(9)°, γ = 91.847(9)°. The compounds Ag_{1 ? x} Mg_{1 ? x} Al_{1 + x} (MoO₄)₃ and AgMg₃Al(MoO₄)₅ are thermally stable up to 790 and 820°C, respectively.     

Mixed Valence Tungsten(IV,V) Compounds with Layered Structures (Part II)): Synthesis and Crystal Structures of Cu1−x[W2O2Cl6] and Cu1−x[W4O4Cl10]

The reaction of CuCl with WOCl₃ at 400 °C leads to a mixture of Cu_1?x[W₂O₂Cl₆] ( 1 ) and Cu_1?x[W₄O₄Cl₁₀] ( 2 ) in form of black lustrous needles. Both compounds crystallize in space group C2/m with a = 12.7832(5) Å, b = 3.7656(2) Å, c = 10.7362(3) Å, β = 119.169(2)° for 1 and a = 12.8367(19) Å, b = 3.7715(7) Å, c = 15.955(3) Å, β = 102.736(5)° for 2 . The structures are made up of WO₂Cl₄ octahedra. In the case of 1 two octahedra are edge‐sharing via chlorine atoms to form pairs which are linked via the trans‐positioned oxygen atoms to form infinite double strands . In the structure of 2 two of these double strands are condensed via terminal chlorine atoms to form quadruple strands . Like for all members of the M_x[W₂O₂X₆] structure family (X = Cl, Br) nonstochiometry with respect to the cations M was observed. The copper content of 1 and 2 was derived from the site occupation factors of the respective structure refinements. For several crystals examined the copper content varied between x = 0.27 and 0.17 for 1 and x = 0.04 for 2 . In both structures the oxochlorotungstate strands are negatively charged and connected to layers by the monovalent copper ions, which are tetrahedrally coordinated by the non‐bridging chlorine atoms of the strands. The structure models imply disorder of the Cu⁺ ions over closely neighboured sites.     

Synthesis and structure of alkali metal zirconium vanadate phosphates

Mixed vanadate phosphates in the systems MZr₂(VO₄) _x (PO₄)_{3 ? x} , where M is an alkali metal, were synthesized and studied by X-ray diffraction, electron probe microanalysis, and IR spectroscopy. Substitutional solid solutions with the structure of the mineral kosnarite (NZP) are formed at the compositions 0 ≤ x ≤ 0.2 for M = Li; 0 ≤ x ≤ 0.4 for M = Na; 0 ≤ x ≤ 0.5 for M = K; 0 ≤ x ≤ 0.3 for M = Rb; and 0 ≤ x ≤ 0.2 for M = Cs. Apart from the high-temperature NZP modification, lithium vanadate phosphates LiZr₂(VO₄) _x (PO₄)_{3 ? x} with 0 ≤ x ≤ 0.8 synthesized at temperatures not exceeding 840°C crystallize in the scandium tungstate type structure. The crystal structures of LiZr₂(VO₄)_0.8(PO₄)_2.2 (space group P2₁/n, a = 8.8447(6) Å, b = 8.9876(7) Å, c = 12.3976(7) Å, β = 90.821(4)○, V = 985.4(1) ų, Z = 4) and NaZr₂(VO₄)_0.4(PO₄)_2.6 (space group $R\bar 3c$ = 8.8182(3) Å, c = 22.7814(6) Å, V = 1534.14(1) ų, Z = 6) were refined by the Rietvield method. The framework of the vanadate phosphate structure is composed of tetrahedra (that are statistically occupied by vanadium and phosphorus atoms) and ZrO₆ octahedra. The alkali metal atoms occupy extra-framework sites.     

Mössbauer studies of Fe x Zn1−x (4-amino-1,2,4-triazole)3(NO3)2 complexes possessing the1 A 1⇄5 T 2 spin transition

Mössbauer studies were carried out for the mixed complexes Fe_xZn_1?x(ATr)₃(NO₃)₂ (0.2≤x≤1) having a polynuclear chain structure, for which we had earlier found a significant decrease in the¹A₁ ⁵T₂ spin transition temperature when iron was replaced with zinc. For these complexes, we have found for the first time a tendency toward an increase in the chemical shifts and quadrupole splitting of iron atoms in the low-spin state with the degree of their replacement by other metal atoms. A correlation between these Mössbauer spectral data and the spin transition temperature was found. The results of these studies are explained in terms of the model of steric strains in molecular fragments of the chain structure of the complexes appearing when iron atoms are replaced by zinc atoms.