Crystal structure and magnetic properties of Cu4NiSi2S7

The structure of the compound Cu₄NiSi₂S₇ has been determined. It crystallizes in a new, monoclinic distorted sphalerite superlattice with the parameters: $\text{a}\text{= 11.551}\text{A}\text{?}$, $\text{b}\text{= 5.313}\text{A}\text{?}$, $\text{c}\text{= 8.165}\text{A}\text{?}$, β = 98.72°, $\text{V}\text{= 495.2}\text{A}\text{?}{}^3$, Z = 2, space group C2. The analogous compound Cu₄NiGe₂S₇ is isotypic. At a Neél temperature T_N = 20.2 K, Cu₄NiSi₂S₇ becomes antiferromagnetic. The magnetic moment of the paramagnetic phase is 2.6μ_B.     

Superconductivity of ternary sulfides and the structure of PbMo6S8

The compound Pb_0.92Mo₆S_7.5, a derivation from the ideal stoichiometric compound PbMo₆S₈, is a member of the ternary sulfide series M_XMo₃S₄ where M = Ag, Sn, Ca, Sr, Pb, Ba, Cd, Zn, Mg, Cu, Mn, Cr, Fe, Co, Ni, Li, Na, Sc, and Y. Members of the series with M = Pb, Sn, Ag, Cu, Zn, Mg, Cd, Sc and Y have been found to be superconducting at T_C = 15.2, 14.2, 9.1, 10.9, 3.6, 3.5, 3.5, 3.6 and 3.0^oK respectively. The lead compound has rhombohedral symmetry R3?, lattice parameters $\text{a}\text{= 6.551}\text{A}\text{?}$ and α = 89.33°, and one formula per unit cell. The structure consists of a distorted primitive-cubic network of sulfur atoms with every fourth sulfur cube occupied by either a Pb atom or a Mo₆ octahedron. The vertices of the Mo₆ octahedron lie in the face centers of the sulfur cube which is tilted approximately 15^o with respect to the rhombohedral axes. This arrangement yields open channels running through the structure parallel to the unit cell edges.     

Phase investigations in the system PbSIn2S3 and the crystal structures of PbIn2S4 and Pb6In10S21

The system PbS-In₂S₃ was examined by differential thermal analysis (DTA), chemical vapour transport (CVT), and X-ray diffraction. Five new phases of compositions closely related to the 1:1 ratio were found and prepared as needle-shaped single-crystals; their crystal data are reported. The structures of PbIn₂S₄ (orthorhombic, Pnma, a=11.688(1), b=3.8528(1), $\text{c}\text{=13.763(1)}\text{A}\text{?}$, Z=4) and Pb₆In₁₀S₂₁ (monoclinic, C2/m, a=27.629(3), b=3.8630(5), $\text{c}\text{=15.705(2)}\text{A}\text{?}$, β=95.9°, Z=2 were solved from 808 resp. 3554 independent reflexions and refined to R=0.116 resp. 0.068. In both structures the In-S coordination polyhedra are distorted octahedra, the Pb-S polyhedra are distorted bicapped trigonal prisms.     

Structure cristalline de Mn0, 4Er4, 6S7

The crystal structure of Mn₀, ₄Er₄, ₆S₇ ($\text{a}\text{= 12,573 (4)}\text{A}\text{?}$, $\text{b}\text{= 11,390 (4)}\text{A}\text{?}$, $\text{c}\text{= 3,777 (4)}\text{A}\text{?}$, γ = 105,45°, space group B2/m, Z = 2) has been refined by a least square method to a final R = 0,045, with 1431 independant reflections. The octahedral positions are occupied either by Er and Mn atoms or by Er atoms only and the prismatic sites by Er atoms.     

Preparation and characterization of the mixed oxide V9Mo6O40

The β phase in the V₂O₅-MoO₃ system has been prepared and its composition determined to be V₉Mo₆O₄₀. The monoclinic unit cell dimensions, determined from X-ray powder data are $\text{a}\text{= 19.365(3)}\text{A}\text{?}$, $\text{b}\text{= 3.626(1)}\text{A}\text{?}$, $\text{c}\text{= 4.124(1)}\text{A}\text{?}$ and β = 90.61°.     

Crystal data for two new phosphate-tellurates : Te(OH)6·2TlH2PO4·Tl2HPO4 and Te(OH)6·2TlH2PO4. Crystal structure of Te(OH)6·2TlH2PO4

We describe chemical preparations and give crystal data for two new phosphate-tellurates : Te(OH)₆·2TlH₂PO₄·Tl₂HPO₄ and Te(OH)₆·2TlH₂PO₄. Both are monoclinic with the following unit cell dimensions : a = 13.68(1), b = 6.317(5), $\text{c}\text{= 11.36(1)}\text{A}\text{?}$, β = 110.18(1)°, Z = 2, D_x = 4.82, S.G. = Cm for the first one, a = 6.285(5), b = 14.74(1), $\text{c}\text{= 7.844(5)}\text{A}\text{?}$, β = 113.38(1)°, Z = 2, D_x = 4.14, S.G. = P2₁/n for the second one. Crystal structure of the second salt shows, as in the already described phosphate-tellurates, the coexistence of independent TeO₆ octahedra and PO₄ tetrahedra in the atomic arrangement.     

Stable Po2-region of ordered perovskites Ca2FeMoO6 and Sr2FeMoO6 at 1200°C

Stable Po₂-region of the title compounds at 1200°C has been determined via an isothermal gravimetry. Ca₂FeMoO₆ was stable within the region $\text{?8.9 ≧}\text{log Po}{}_2\text{≧ ?12.5}$, decomposed by reduction into a triphasic mixture of CaO + Mo + ε-Fe₃Mo₂, and by oxidation into a biphasic mixture of CaMoO₄ (Scheelite structure) + CaFeO_2.5 (Brownmillerite structure). Sr₂FeMoO₆ was stable within the region $\text{?9.8 ≧}\text{log Po}{}_2\text{≧ ?13.5}$, decomposed by reduction into SrO + Mo + ε-Fe₃Mo₂ and by oxidation into SrMoO₄ (Scheelite structure) + SrMoO_3?x (non-stoichiometric perovskite structure).     

Systeme Ga2S3PbS diagramme de phase,etude cristallographique

Four intermediate phases are present ; PbGa₂S₄,orthorombic EuGa₂S₄-type (a = 20,44 ; b = 20,64 ; $\text{c}\text{= 12,09}\text{A}\text{?}$) ; Pb₂Ga₂S₅, orthorombic space group Pbca (a = 12,38 ; b = 11,90 ; $\text{c}\text{= 11,03}\text{A}\text{?}$) ; and two Ga₂S₃-rich solid solutions, one of the wurtzite type at temperatures above 1000°C, one of the distorded blende type below about 970°C. PbGa₂S₄ has a peritectic decomposition at 930°C, and Pb₂Ga₂S₅ at 900 ± 5°C. The eutectic is at 730°C for about n = 0,80 ($\text{n}\text{=}\text{Pb}\text{Pb+Ga}$ atomic). A glassy region is obtained by quenching the liquid phase and its extent depends on the quenching temperature (at 1000°C, between n = 0,25 and n = 0,50).     

Crystal structures of two cesium phosphate-tellurates : Te(OH)6.Cs2HPO4 and Te(OH)6.Cs2HPO4.2CsH2PO4

Te(OH)₆.Cs₂HPO₄ and Te(OH)₆.Cs₂HPO₄.2CsH₂PO₄ are monoclinic, the first one with a = 8.204(5), b = 18.416(9), $\text{c}\text{= 6.995(5)}\text{A}\text{?}$, β = 89.89(5)°, Z = 4, space group P2₁/n, the second one with a = 9.591(6), b = 13.163(9), $\text{c}\text{= 8.367(5)}\text{A}\text{?}$, β = 106.27(5)°, Z = 2, space group P2₁/m. As already observed in previously described phosphate-tellurates the main feature of these atomic arrangements is the coexistence of two independent and different types of anions (PO₄ and TeO₆ groups) in the unit cell.     

The preparation,crystal structures and properties of the potassium vanadium sulfides KXV5S8 (0.5≦x≦0.7)

The crystal structures of the potassium vanadium sulphides K_0.7V₅S₈ and K_0.5V₅S₈ (=KV₁₀S₁₆) have been determined. K_0.7V₅S₈ has a C-centered monoclinic unit cell of dimensions $\text{a}\text{=17.499(3)}\text{A}\text{?}$, $\text{b}\text{=3.2986(6)}\text{A}\text{?}$, $\text{c}\text{=8.489(1)}\text{A}\text{?}$, ß=103.98(1)°, spacegroup C2/m; isomorphous with TIV₅S₈; K_0.5V₅S₈ has essentially the same structure, but due to ordering of the K atoms, the monoclinic b-axis is doubled, thus forming a superstructure. The cell parameters are: $\text{a}\text{=17.462(4)}\text{A}\text{?}$, $\text{b}\text{=6.556(2)}\text{A}\text{?}$, $\text{c}\text{=8.4595(9)}\text{A}\text{?}$, ß=103.86(1)°, spacegroup P2. The structures are characterized by a three-dimensional framework of VS₆ octahedra with channels in which the K atoms are situated. Both compounds exhibit metallic behaviour.     

Etude structurale d'un thiohalogenure supra conducteur derivant du Mo(II) : Mo6S6Br2

The X-ray structure of Mo₆S₆Br₂, isostructural with Mo₆Se₈ (space group R$\text{3}$), has been determined from three dimensional single crystal counter data and refined to a final R value of 0.044 for 482 independent reflections. Six sulfur atoms are located on the 6f site, whereas the bromine atoms are located on the 2c site, this later one being slightly deficient. The structural data are compared with M_xMo₆S₈ ones, related to the high thermal stability of this compound and correlated with the high superconducting critical temperature.     

Preparation,properties and crystal structure of TlV5S8

A new sulfide of vanadium and thallium TlV₅S₈ has been prepared. It has monoclinic symmetry with space group C2 and cell dimensions: $\text{a}\text{= 17.465}\text{A}\text{?}$, $\text{b}\text{= 3.301}\text{A}\text{?}$, $\text{c}\text{= 8.519}\text{A}\text{?}$ and β = 103.94°. The structure can be described as a 3D framework made up of infinite layers and double chains which consist of VS₆ octahedra sharing faces and edges. Large rectangular tunnels host the thallium atoms. The compound shows metallic behavior.     

Crystal structure of K4[H2J2O10].8H20

Crystals of K₄ [H₂J₂O₁₀] 8H₂O belong to the triclinic system, space group P 1 with a = 7.161 (2) $\text{A}\text{?}\text{, b}\text{= 10,553}$ (5) $\text{A}\text{?}\text{, c}\text{= 7,081}$ (2) $\text{A}\text{?}\text{, α = 98°1′}$, β = 117°8′, γ = 90°6′ and Z = 1. The crystal structure has been determined on the basis of photographic data from 877 independent reflections, with the final R value of 6,6%. The iodine atoms are surrounded by a distorted octahedra consisting of five oxygen atoms and one OH group. The average J-O distance is 2.03 Å. There are 2 independent K atoms in the structure. K(1) has a coordination number of eight, while K(2) is surrounded by 6 (5 water molecules + one OH group) nearest neighbours.     

Epitaxial intergrowth of the layered crystals SnTaS2 and SnS2

Layered crystals were obtained, with an overall composition of about Sn₃Ta₂S₆, which gave unusual electron diffraction patterns. The patterns are explained in terms of an intergrowth of thin, alternating layers of SnTaS₂ and epitaxially deformed SnS₂. The SnS₂ has a monoclinic structure with $\text{a}\text{= 15.78}\text{A}\text{?}$, $\text{b}\text{= 5.67}\text{A}\text{?}$ and β = 95°. Similar crystals based on Nb rather than Ta have also been obtained.     

Etude du systeme KPO3-LaP3O9. Donnees cristal lographiques sur K2La(PO3)5 et (NH4)2La(PO3)5

The system KPO₃-LaP₃O₉ has been studied for the first time by differential thermal analysis and X ray diffraction. The system shows two compounds KLa(PO₃)₄ and K₂La(PO₃)₅ which melt in a peritectic decomposition at 880°C and 770°C respectively. An eutectic point appears at 705°C; The eutectic point corresponds to a concentration of 10% molar LaP₃O₉.Infra Red absorption spectra are typical of chain phosphates.The new compound K₂La(PO₃₅ is isotypic whith (NH₄)₂La(PO₃)₅ which has been synthetized for the first time. They belong to the triclinic system whith space group P1 and Z = 2. The parameters of the unit cell are: $\text{a = 7.309(4)}\text{A}\text{?}$$\text{b = 13.35(2)}\text{A}\text{?}$$\text{c = 7.155(7)}\text{A}\text{?}$α = 90°3(1) β = 109°17(7) γ = 89°90(4) for K₂La(PO₃)₅ and: $\text{a = 7.174(8)}\text{A}\text{?}$$\text{b = 13.38(2)}\text{A}\text{?}$$\text{c = 7.35(2)}\text{A}\text{?}$α = 90°6(2) β = 107°4(1) γ = 89°82(7) for (NH₄)₂La(PO₃)₅.     

The many phases of HUP, (UO2)[HPO4] · 4H2O. An electron-optical investigation

The prompt recrystallization of the tetragonal phyllophosphate HUP, (UO₂)[HPO₄] · 4H₂O, when rinsed with distilled water at ambient temperature, has been studied by TEM, SEM and SAD. In course of the rinsing process, to remove excess phosphorous acid, HUP underwent an orthorhombic phase change, which produced two orthorhombic phases O₁ and O₂. O₁ has $\text{a = 7.6(3)}\text{A}\text{?}$, $\text{c = 7.0(4)}\text{A}\text{?}$, and 001 absent for l odd. O₂ has $\text{a = 7.3(2)}\text{A}\text{?}$, $\text{c = 6.8(2)}\text{A}\text{?}$ and no systematic absent reflections. O₁ and O₂ are metastable and by spinodal decomposition modulate into monoclinic phases through a string of intermediate and disordered phases with the β-angle increasing from 90.0° (orthorhombic phases) to 91.3(3)°, 95(2)° and 97.7(2)° for M_2.2, M_2.1, and M_1.1 respectively, where M_1.1 is the monoclinic derivative ($\text{a = 6.9(4)}\text{A}\text{?}$, $\text{c = 6.4(4)}\text{A}\text{?}$, β = 97.7(3)°) of O₁ and M_2.1 ($\text{a = 7.3(4)}\text{A}\text{?}$, $\text{c = 12.1(3)}\text{A}\text{?}$, β = 95(2)°) together with M_2.2 ($\text{a = 14.22(4)}\text{A}\text{?}$, $\text{c = 13.08(4)}\text{A}\text{?}$, β = 91.3(3)°) are the derivatives of O₂. The crystallographic b axis could not be determined. All the abovementioned phases exhibit a striking epitaxial relationship which presumably gives the clue to the fact that these phase findings are at variance with X-ray findings given in literature. It is suggested that the phases are isomeric polymorphs of HUP.     

An outline of the crystal-structure of Bi2Mo2O9

An outline of the structure of the catalyser component Bi₂Mo₂O₉ has been determined from X-ray powder diffractometer diagrams. The space group is $\text{P}{}^2\text{l}\text{n}$ ($\text{=}\text{P}{}^2\text{l}\text{c}$) with cell constants: $\text{a}\text{= 11.946 (2)}\text{A}\text{?}$, $\text{b}\text{= 10.795 (2)}\text{A}\text{?}$, $\text{c}\text{= 11.876 (2)}\text{A}\text{?}$ and β = 90.15 (2)°. There are eight formula units per cell. The positions of the metal-ions could directly be derived from the intensities of the strongest reflexions. With difference terms calculated from 19 strong reflexions a Δ F-synthesis was calculated, which revealed the approximate positions of the O^2?-ions. From packing considerations it was apparent that of 9 0^2?-ions one is only coordinated by Bi³⁺ and that Mo⁶⁺ must be tetrahedrally surrounded by 0^2?. These tetrahedra may be strongly distorted. The structure is not related to the scheelite-structure as has been assumed by some authors.     

New tetrahedrally coordinated A2CdBr4 compounds (A = Cs,CH3NH3)

(CH₃NH₃)₂CdBr₄ and Cs₂CdBr₄ are two compounds with a tetrahedral CdBr₄-coordination. Their room temperature structures are determined. (CH₃NH₃)₂CdBr₄: monoclinic, $\text{P}\text{2}{}_1\text{c}$, $\text{a}\text{= 8.1227(13)}\text{A}\text{?}$, $\text{b}\text{= 13.4355(16)}\text{A}\text{?}$, $\text{c}\text{= 11.4194(13)}\text{A}\text{?}$, β = 96.194(11) °, z = 4. Cs₂CdBr₄: orthorhombic, Pnma, $\text{a}\text{= 10.235(5)}\text{A}\text{?}$, $\text{b}\text{= 7.946(3)}\text{A}\text{?}$, $\text{c}\text{= 13.977(5)}\text{A}\text{?}$, z = 4.     

New ternary molybdenum chalcogenides containing Mo6 and Mo9 clusters: M2Mo15Se19 (M = K,Ba, In,Tl) and K2Mo15S19

New superconducting Mo^II compounds M₂Mo₁₅X₁₉ (M = K, Ba, In, Tl and X = Se; M = K and X = S have been found. These materials crystallize in a new structural type containing isolated Mo₆X₈ and Mo₉X₁₁ units. They are superconducting (T_c = 3.32 K for K₂Mo₁₅S₁₉), and have high initial slopes $\text{dHc}{}_2\text{dT}$ of the upper critical field.     

Oligoselenidogermanate (III): Zur kenntnis von Na6Ge2Se6 und Na8Ge4Se10

The following new oligomeric selenidogermanates (III) have been prepared and structurally characterized: Na₆Ge₂Se₆: monoclinic, space group $\text{P}\text{2}{}_1\text{c}$ (No. 14) a = 836.7(5) pm, b = 1192.4(8) pm, c = 815.8(5) pmβ = 118.63(15)°.The compound is isotypic to K₆Sn₂Te₆, essential structure elements are [Ge₂Se₆]^6? anions.Na₈Ge₄Se₁₀: triclinic, space group P1? (No. 2) a = 707.4(5) pm, b = 809.8(5) pm, c = 1065.7(6) pmα = 73.44(15)°, β = 70.84(15)°, ?= 81.73(15)°Two Ge₂Se₆ octahedra are connected by a common edge forming a six-membered cyclic [(GeSe₂)₄Se₂]^8? anion.