Crystal growth and properties of lead pyrophosphate,Pb2P2O7

Single crystals of Pb₂P₂O₇ have been grown by the Czochralski technique. They have the triclinic space group $\text{P}\text{1}$ with cell dimensions a = 6.9627 Å, b = 6.9754Å, c = 12.764 Å, α = 96.78°, β = 91.16°, γ = 89.68°. There are four molecules per unit cell. Dielectric properties for this compound have been measured and are discussed.     

Crystal growth and X-ray data of the lead phosphates Pb4P2O9 and Pb8P2O13

Single crystals of the title compounds have been grown by the Czochralski technique. Pb₄P₂O₉ crystallizes in the space group $\text{P2}{}_1\text{c}$ with the parameters a = 9.4812 Å, b = 7.1303 Å, c = 14.390 Å, β = 104.51° and Pb₈P₂O₁₃ in $\text{C2}\text{m}$ with a = 10.641 Å, b = 10.206Å c = 14.342 Å, β = 98.34°.     

Polyèdre de coordination de l'etain(II) dans SnC2O4: Relations structurales entre SnC2O4, Na2C2O4 et Na2Sn(C2O4)2

The crystal structure of SnC₂O₄ has been determined by X-ray single-crystal techniques and refined to R = 0,018 for 1139 reflections. The cell is monoclinic, space group $\text{C2}\text{c}$ with Z = 4 formula units, the parameters being a = 10,375(3)Å. b = 5,504(2)Å, c = 8,234(3)Å, β = 125,11(2)°. The oxalato groups, located on symmetry centers, are chelated to two Sn atoms through one oxygen on each carbon atom, giving rise to an infinite string (SnC₂O₄)_n. The Sn(II) atom is one-side bonded to four oxygen atoms with two SnO bonds of 2,232(2) Å and two of 2,393(2) Å. The tin atom is in a distorted trigonal bipyramid SnO₄E, the lone pair E occupying one of the apices of the equatorial trigonal base of the polyhedron. Crystal structure comparison with disodium bisoxalatostannate(II), Na₂Sn(C₂O₄)₂, permits one to deduce SnC₂O₄ by crystallographic shear operation $\text{1}\text{8}\text{[34}\text{2}\text{](001)}$ of $\text{c}\text{2}$ periodicity. Na₂Sn(C₂O₄)₂ can be described as an intergrowth of SnC₂O₄ and Na₂C₂O₄ structures and consldered as the first member of a new series Na₂Sn_1+n(C₂O₄)_2+n with n integer ? 0.     

The crystal structure of a complex cerium(III) molybdate; Ce6(MoO4)8(Mo2O7)

Ce₆Mo₁₀O₃₉ crystallizes in the triclinic system with unit-cell dimensions (from single-crystal data) a = 10.148(5), Å, b = 18.764(6), Å, c = 9.566(5), Å, α = 103.12(7)°, β = 78.07(7)°, γ = 107.69(7)°, and space group $\text{P}\text{1}\text{, z = 2}$. The structure was solved using direct methods with 3113 countermeasured reflections (MoKα radiation), and refined using Fourier and least-squares techniques to a conventional R of 0.039 (ωR = 0.047). Ce₆Mo₁₀O₃₉ has a structure that consists of isolated MoO₄ tetrahedra together with one corner-shared pair of tetrahedra, linked to irregular eight-coordinate Ce(III) polyhedra. The average MoO distance of 1.77 Å, and average CeO distance of 2.52 Å are in good agreement with previously reported values.     

Structural studies in the Li2MoO4MoO3 system: Part 1 the low temperature form of lithium tetramolybdate,LLi2Mo4O13

LLi₂Mo₄o₁₃ crystallizes in the triclinic system with unit-cell dimensions a = 8.578 Å, b = 11.450 Å, c = 8.225 Å, α = 109.24°, β = 96.04°, γ = 95.95° and space group $\text{P}\text{1}\text{, Z = 3}$. The calculated and measured densities are 4.02 g/cm³ and 4.1 g/cm³ respectively. The structure was solved using three-dimensional Patterson and Fourier techniques. Of the 2468 unique reflections collected by counter methods, 1813 with I ? 3σ(I) were used in the least-squares refinement of the model to a conventional R of 0.031 (ωR = 0.038). LLi₂Mo₄O₁₃ is a derivative of the V₆O₁₃ structure with oxygen ions arranged in a face-centred cubic type array with octahedrally coordinated molybdenum and lithium ions ordered into layers.     

Structure cristalline de Cu4(PO4)2O

Cu₄(PO₄)₂O is a new copper-rich phosphate. The preparation is described. The unit cell is triclinic, $\text{P}\text{1}$, with a = 7.528 Å, b = 8.090 Å, c = 6.272 Å; α = 113.68°, β = 81.56°, γ = 105.77°. The structure was solved from 1526 independent reflections using Patterson and Fourier syntheses. The final R value is 0.041 for the 1217 strongest reflections. Copper sites form a three-dimensional framework. The structure consists of homogeneous layers of copper and oxygen atoms parallel to the (012) plane. Phosphorus atoms are inserted between copper and oxygen layers.     

The crystal structure of Cu4(PO4)2O

Cu₄(PO₄)₂O crystallizes in the space group $\text{P}\text{1}$ with a = 7.5393(8) Å, b = 8.1021(9) Å, c = 6.2764(8) Å, α = 113.65(1)°, β = 98.42(1)° and γ = 74.19(1)°. The structure was refined by full-matrix least-squares techniques using automatic diffractometer data to R = 0.046 (R_w = 0.056). Four unique copper atoms are in six, five-, and four-coordinated polyhedra which are linked together to form a three-dimensional network. The structure is best described in terms of a cubic close-packed array of oxygen atoms with one-tenth of the possible anion sites vacant.     

Die molekül- und kristallstruktur von thallium-tris(bistrimethylsilylamin), Tl[N(SiMe3)2]3

The molecular and crystal structure of tris(bistrimethylsilylamin)thallium was determined by means of single-crystal X-ray spectroscopy: in the space group P$\text{3}$1c with a = 16.447(7), c = 8.456(7) Å; and D_c = 1.149 g cm^?3 two molecules are located in the unit cell. The compound is isomorphous to the analogues Fe[N(SiMe₃)₂]₃ or Al[N(SiMe₃)₂]₃, respectively, which show a propellar-twist of the Si₂N-groups versus the plane of the metal atom and the three nitrogen-atoms: Tl(N)₃/Si₂N 49.1°; SiNSi 122.6°; NSiC 111.8°; CSiC 107.1°; TlN 2.089 Å;; SiN 1.738 Å;; $\text{SiC}$ 1.889 Å;.     

A dichromium(II) compound with an elongated metal-metal bond: Cr2(oxindolate)4(oxindole)2

The title compound has been prepared by reaction of (C₅H₅)₂Cr with oxindole (indole with CO in place of CH₂ at the 2-position). Red single crystals belong to space group P2₁/c with a = 10.107(4) Å, b = 22.496(7) Å, c = 9.210(3) Å, β = 93.26(3)°, V = 2091(2), and Z = 2. The centrosymmetric molecule has a CrCr distance of 2.495(4) Å. The mean CrO and CrN distances for the bonds to bridging oxindolate anions are 2.024(7) and 2.065(8) Å, respectively. There is an oxindole molecule bound at each end with a CrO axial bond of length 2.341(8) Å and a hydrogen bond from the oxindole NH group to an equatorial oxygen atom of length 2.83(1) Å. The significance of this compound with respect to CrCr bonding is discussed.     

Formation of rutile-type Ta(IV)O2 by shock reduction and cation-deficient Ta0.8O2 by subsequent oxidation

Ta₂O₅ is reduced to Ta(IV)O₂ with the rutile structure by shock-loading to 50–60 GPa. Tetragonal unit cell parameters at room conditions are measured to be a = 4.7518(5)Å, c = 3.0878(4) Å, $\text{c}\text{a}\text{= 0.6498(1)}$, and V = 69.72(1) ų. The chemical composition is thermogravimetrically determined to be Ta_0.97±0.04O₂ by heating shock-reduced products in an oxygen gas flow to 1200°C. In the oxidation process a cation-deficient rutile-type compound Ta_0.8O₂ is found to be metastably formed.     

High pressure and high temperature investigations in the system MgOSiO2H2O

The system MgOSiO₂H₂O was investigated at pressures between 40 and 95 kbar and at temperatures between 500 and 1400°C. The reaction products were examined by X-ray, optical and thermal analysis techniques and the density of phase A discovered by Ringwood and Major was also measured. It was found that phase A was hydrated and its chemical formula was H₆Mg₇Si₂O₁₄. When the $\text{Mg}\text{Si}$ ratio of the system is 2, phase A + clinoenstatite, and forsterite are stable at temperatures lower and higher than a boundary curve T (°C) = 10P (kbar), respectively. When the $\text{Mg}\text{Si}$ ratio of the system is 3, phase A + phase D (which is completely different from the phases, A, B and C discovered by Ringwood and Major, and any other known phases of magnesium silicate) and phase D + brucite are stable at temperatures lower and higher than a boundary curve T(°C) = 10P (kbar) + 200. Phase A has approximately an hexagonal symmetry and the space group and the lattice parameters are determined as P6₃ or $\text{P6}{}_3\text{m}$ and a = 7.866(2) Å and c = 9.600(3) Å, respectively. The measured density is 2.96 ± 0.02 g/cm³. The optical observations show that phase A is biaxial positive crystal with refractive indices α = 1.638 ± 0.001, β = 1.640 ± 0.002, and γ = 1.649 ± 0.001. Some interpretation is given on the inconsistency between the symmetry determined by the X-ray diffraction and the optical observation. The new phase D belongs to the space group $\text{P2}{}_1\text{c}$ with lattice parameters a = 7.914(2)Å, b = 4.752(1) Å, c = 10.350(2) Å and β = 108.71(5)° and is a biaxial crystal with refractive indices α = 1.630 ± 0.002, β = 1.642 ± 0.002 and γ = 1.658 ± 0.001.     

Structural changes resulting from doping Ti2O3 with Sc2O3 or Al2O3

The crystal structures of (Ti_1?xSc_x)₂O₃, x = 0.0038, 0.0109, and 0.0413, and of (Ti_0.99Al_0.01)₂O₃, have been determined from X-ray diffraction data collected from single crystals using an automated diffractometer, and have been refined to weighted residuals of 25–34. Cell constants have also been determined for x = 0.0005, 0.0019, and 0.0232. The compounds are rhombohedral, space group $\text{R}\text{3}\text{c}$, and are isomorphous with α-Al₂O₃. The hexagonal cell dimensions range from a = 5.1573(2)Å, c = 13.613(1)Å for (Ti_0.9995Sc_0.0005)₂O₃ to a = 5.1659(4)Å, c = 13.644(1)Å for (Ti_0.9587Sc_0.0413)₂O₃, and a = 5.1526(2)Å, c = 13.609(1)Å for (Ti_0.99Al_0.01)₂O₃. Sc and Al substitution cause similar increases in the short near-neighbor metal-metal distance across the shared octahedral face; for Sc doping the increase is from 2.578(1) Å in pure Ti₂O₃ to 2.597(1) Å in (Ti_0.9587Sc_0.0413)₂O₃. By contrast, changes in the metal-metal distance across the shared octahedral edge appear to be governed by ionic size effects. The distance increases from 2.994(1) Å in Ti₂O₃ to 3.000(1) Å in (Ti_0.9587Sc_0.0413)₂O₃ and decreases to 2.991(1) Å in (Ti_0.99Al_0.01)₂O₃.     

Crystal structures of the fluorite-related phases CaHf4O9 and Ca6Hf19O44

Crystal structures for the fluorite-related phases CaHf₄O₉$\text{ф}{}_1$) and Ca₆Hf₁₉O₄₄ ($\text{ф}{}_2$) have been determined from X-ray powder diffraction data. qf₁ is monoclinic, $\text{C2}\text{c}$, with a = 17.698 Å, b = 14.500Å, c = 12.021 Å, β = 119.47° and Z = 16. qf₂ is rhombohedral, $\text{R}\text{3}\text{c}$, with a = 12.058 Å, α = 98.31° and Z = 2.Both phases are superstructures derived from the defect fluorite structure by ordering of the cations and of the anion vacancies. The ordering is such that the calcium ions are always 8-coordinated by oxygen ions, while the hafnium ions may be 6-, 7-, or 8-coordinated. The closest approach of anion vacancies is a $\text{1}\text{2}\text{〈111〉}$ fluorite subcell vector, and in each structure vacancies with this separation form strings.     

K1.4P4W14O50: An odd-m member (m = 7) of the monophosphate tungsten bronze series KxP4O8(WO3)2m

The crystal structure of K_xP₄W₁₄O₅₀ (x = 1.4) has been solved by three-dimensional single crystal X-ray analysis. The refinement in the cell of symmetry $\text{A2}\text{m}$, with a = 6.660(2) Å, b = 5.3483(3) Å, c = 27.06(5) Å, and β = 97.20(2)°, Z = 1, has led to R = 0.036 and R_w = 0.039 for 2436 reflections with $\text{σ(I)}\text{I}\text{≤ 0.333}$. This structure belongs to the structural family K_xP₄O₈(WO₃)_2m, called monophosphate tungsten bronzes (MPTB), which is characterized by ReO₃-type slabs of various widths connected through PO₄ single tetrahedra. This bronze corresponds to the member m = 7 of the series and its framework is built up alternately of strands of three and four WO₆ octahedra. The structural relationships with the P₄O₈(WO₃)_2m series, called M′PTB, are described and the possibility of intergrowth between these two structures is discussed.     

Structure cristalline du tétramétaphosphate de nickel-ammonium heptahydraté: Ni(NH4)2P4O12 · 7H2O

Nickel-ammonium tetrametaphosphate, Ni(NH₄)₂P₄O₁₂ · 7H₂O is triclinic with a = 13.841(3); b = 9.621(5); c = 7.482(2)Å; α = 98.05(4); β = 97.25(4); γ = 103.01(4)°; M = 536.59; V = 947.9ų; Z = 2; D_x = 1.879 g cm^?3; μ = 14.524 cm^?1, and space group $\text{P}\text{1}$. The crystal structure was solved using 1661 independent reflections measured on a single-crystal diffractometer (MoKα). The final R value is 0.056. The two crystallographic independent nickel atoms Ni(1) and Ni(2) are octahedrally coordinated: Ni(1) by four oxygen atoms and two water molecules, Ni(2) by six water molecules. Ni(1), closely connected to two P₄O₁₂ rings, forms a complex anion [Ni(P₄O₁₂)₂(H₂O)₂]^6? which is associated to ammonium polyhedra and [Ni(H₂O)₆]²⁺ octahedra. Another interesting feature of this atomic arrangement is the presence of a large channel (10 × 4) Ų parallel to the $\text{c}$ axis. The internal surface of this channel is covered by six zeolitic water molecules.     

The crystal structure of Cs[VOF3] · 12H2O

The crystal structure of $\text{Cs[VOF}{}_3\text{]}\text{·}\text{1}\text{2}\text{H}{}_2\text{O}$ has been determined and refined on the basis of three-dimensional X-ray diffractometer data (MoKα radiation). The structure is monoclinic, a = 7.710(2), b = 19.474(7), c = 7.216(2)Å, β = 116.75(1)°, V = 967.5ų, Z =8, space group Cc (No. 9). The final R and R_w were 0.0295 and 0.0300, respectively, for 1356 independent reflections and 117 variables.The structure contains two crystallographically different VOF₅ octahedra linked so as to form complex chains. Two non-equivalent octahedra share one FF edge, forming V₂O₂F₈ doublets. Two F atoms, connected to different V atoms within the doublet, form an edge in the adjacent equivalent V₂O₂F₈ unit thus continuing the chain. The VO distances are 1.583(7) and 1.595(7) Å. The VF distances are in the range 1.881-2.205 Å, mean value: 1.989 Å. The H₂O group is a crystal water molecule.     

The crystal and molecular structure of tris(ortho-aminobenzoato)aquoyttrium(III), Y(H2NC6H4COO)3 · H2O

Tris(ortho-aminobenzoato)aquoyttrium(III), Y(H₂NC₆H₄COO)₃ · H₂O, crystallizes in the monoclinic space group, $\text{C2}\text{c}$, with eight molecules in a unit cell of dimensions: a = 30.89(1) Å, b = 9.09(1) Å, c = 14.85(1) Å, and β = 109.3(1)°. The structure was determined using three-dimensional X-ray diffraction data gathered on multiple-film equi-inclination, integrated Weissenberg, and precession photographs taken about two crystal axes. The structure, excluding the hydrogen atoms, was solved from Patterson and electron density maps and refined by least-squares methods to a final R of 0.081. The coordination about the yttrium atom is sevenfold, best described by a capped trigonal prism. Each ortho-aminobenzoate ligand acts as a bridging bidentate ligand, resulting in six ortho-aminobenzoate residues coupled to each yttrium atom. The water molecule occupies the seventh position. This bonding configuration generates a structure in which each yttrium atom in (100) is attached to two other yttrium atoms via carboxylate bridges to give parallel sets of polymeric chains coincident with (100). It is suggested that this polymeric character accounts for the extreme insolubility of Y(H₂NC₆H₄COO)₃ · H₂O.     

(NH4)4P4O12 · 2Te(OH)6 · 2H2O,the first example of a tetrametaphosphate-tellurate

Ammonium tetrametaphosphate-tellurate dihydrate, (NH₄)₄P₄O₁₂ · 2Te(OH)₆ · 2H₂O, is triclinic with the following unit cell dimensions: a = 11.845(6), b = 8.554(5), c = 7.433(5) Å, α = 66.28(5), β = 95.91(5), γ = 76.00(5)° space group: $\text{P}\text{1}$ and Z = 1. The crystal structure has been determined with a final R value of 0.021. As in the previously described phosphate-tellurates, monophosphate-tellurate and trimetaphosphate-tellurates, the phosphoric anion (here the P₄O₁₂ ring) is independent of the octahedral Te(OH)₆ group. A complete pattern of the hydrogen bonds is given.     

The crystal structure of Na7Mg4.5(P2O7)4

The crystal structure of Na₇Mg_4.5(P₂O₇)₄ has been solved by direct methods from the three-dimensional X-ray data. The space group is $\text{P}\text{1}$. The crystal structure consists of Mg²⁺, Na⁺, and P₂O^4?₇ ions. One magnesium atom at symmetry center (0,0,0) and two sodium atoms at ±(?0.0421, ?0.0596, 0.2230) display occupation factors 0.5 each. A short interatomic distance between these Na⁺ and Mg²⁺ ions (1.80 ± 0.01 Å) excludes the occupation of both sites in the same unit cell. The crystal structure of Na₇Mg_4.5(P₂O₇)₄ consists of unit cells containing Na₈Mg₄(P₂O₇)₄ or Na₆Mg₅(P₂O₇)₄ with a statistical occurrence 1:1.Each Mg²⁺ ion is octahedrally coordinated by six O^2? ions at distances 1.979 – 2.270 Å. The coordination polyhedra around the Na⁺ ions are ill-defined. The bond angles POP in the P₂O^4?₇ groups are 126.6 and 133.6° (±0.3°). The final reliability factor R is 7.1%.     

Crystal structure of a barium-zinc decametaphosphate Ba2Zn3P10O30

Barium-zinc decametaphosphate, Ba₂Zn₃P₁₀O₃₀, is monoclinic, $\text{P2}\text{n}$, with the unit cell parameters a = 21.738(15), b = 5.356(5), c = 10.748(8) Å, β = 99.65(3)° and Z = 2. The crystal structure was solved with a final R value of 0.041. This salt provides the first structural evidence for the existence of a 10-phosphorus ring anion.