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°.     

L'oxyde double TeVO4 II. Structure cristalline de TeVO4-β-relations structurales

β-TeVO₄ crystallizes in the monoclinic system with the space group $\text{P2}{}_1\text{c}$ and the parameters: a = 4.379 Å, b = 13.502 Å, c = 5.446 Å, and β = 91.72°. Vanadium occupies the center of a square pyramid of oxygens, an extra oxygen is at VO = 2.77 Å. These distorted octahedra share corners forming puckered sheets parallel to (010). The sheets are held together by [Te₂O₆]^4? groups in which tellurium is one-side coordinated by four oxygen atoms.     

New SbS2 strings in the BaSb2S4 structure

The new compound BaSb₂S₄ crystallizes in the monoclinic system (space group: $\text{P2}{}_1\text{c}$, No. 14) with a = 8.985(2) Å, b = 8.203(3) Å, c = 20.602(5) Å, β = 101.36(3)°. SbS₃ ψ tetrahedra and ψ-trigonal SbS₄ bipyramids are connected by common corners and edgers to infinite strings. These are arraged cross-wise in sheets perpendicular to the c axis.     

Crystal structure of Na3PO4 · 12H2O

The crystal structure of trisodium monophosphate hemihydrate was determined. The space group is $\text{C2}\text{c}$ and a unit cell contains eight formula units. The unit cell dimensions of $\text{Na}{}_3\text{PO}{}_4\text{·}\text{1}\text{2}\text{H}{}_2\text{O}$ are a = 9.631(3), b = 5.416(2), c = 16.938(8) Å, β = 102.60(5)°. The final R value is 0.027 for a set of 1430 independent reflections. This atomic arrangement is mainly a three-dimensional network of distorted NaO₆ octahedra. The hydrogen bonding scheme is given.     

Ternary chalcogenide compounds AB2X4: The crystal structures of SiPb2S4 and SiPb2Se4

The crystal structures of SiPb₂S₄ and SiPb₂Se₄ were determined from three dimensional X-ray diffraction data collected with Mo radiation. Both structures are monoclinic with space group $\text{P2}{}_1\text{c}$ and 4 formula units per unit cell. Lattice dimensions for SiPb₂S₄ are a = 6.4721(5) Å, b = 6.6344(9) Å, c = 16.832(1) Å, and β = 108.805(7)°. For SiPb₂Se₄, a = 8.5670(2) Å, b = 7.0745(3) Å, c = 13.6160(3) Å, and β = 108.355(3)°. The Si is tetrahedrally coordinated to S and Se with SiS about 2.10 Å and SiSe about 2.27 Å. The structural framework can be described as consisting of trigonal prisms of S or Se atoms which form a prismatic tube by sharing the triangular faces. These tubes in turn share edges to form corrugated sheets, with the unshared edges projecting alternately on each side of the sheet. The structures are very similar but not identical. In the sulfide one Pb is in sevenfold coordination and the other crystallographically independent Pb is in eightfold coordination. The PbS distances range from 2.82–3.50 Å. In SiPb₂Se₄ both Pb atoms are in sevenfold coordination. PbSe distances range from 2.97 to 3.54 Å. In the sulfide the Pb atoms form a zig-zag chain within the channels formed by the prismatic tubes while in the selenide they are in a straight line.     

The GdPS structure,a new PbFCl-type derivative

The structure of GdPS is orthorhombic, space group Pmnb; a = 5.3620(5), b = 5.4079(6), c = 16.742(2)Å, Z = 8. It is a distorted derivative of the tetragonal PbFCl structure (a₀, c₀) with $\text{a ≈ b ≈ 2}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{a}{}_0\text{, c = 2c}{}_0$. The distortions are due to the formation of phosphorus chains. This structure type is found also in other rare-earth sulfopolyphosphides, e.g., with Ln = La···Sm, Tb···Tm, Y.     

Etude de la tétracoordination de l'etain dans deux orthothiostannates: Na4SnS4 et Ba2SnS4 (α)

The crystal structure of Na₄SnS₄ and Ba₂SnS₄ (α) were determined.Na₄SnS₄ crystallizes in tetragonal system, space group $\text{P}\text{4}\text{2}{}_1\text{c}$ with parameters a = 7.837 Å, c = 6.950 Å, Z = 2 and Ba₂SnS₄ (α) in the monoclinic system, space group $\text{P2}{}_1\text{c}$ with a = 8.481 Å, b = 8.526 Å, c = 12.280 Å, β = 112.97° and Z = 4.In these compounds, the crystal structure is built up from discrete orthothiostannate tetrahedra SnS₄. The structure of Ba₂SnS₄ (α) is modified K₂SO₄β type.     

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.     

Transition metal iodates. IV. Crystallographic,magnetic and nonlinear optic survey of the copper iodates

Three anhydrous polymorphs of cupric iodate, two hydrates, and the basic iodate salesite have been investigated. α-Cu(IO₃)₂ is monoclinic, space group P2₁, with a = 5.551 ± 0.008, b = 5.101 ± 0.004, c = 9.226 ± 0.010 Å and β = 95°4′ ± 11′, with two formulas in the unit cell. Below Θ_N = 8.5 K, α-Cu(IO₃)₂ is antiferromagnetic and also pyroelectric. β-Cu(IO₃)₂ is triclinic, space group $\text{P}\text{1}$, with a = 11.230 ± 0.006, b = 11.368 ± 0.009, c = 10.630 ± 0.009 Å, α = 99°18.3′ ± 0.3′, β = 107°0.4′ ± 0.2′ and γ = 114°23.8′ ± 0.2′ and eight formulas per unit cell: the crystal is paramagnetic to 1.4K. γ-Cu(IO₃)₂ is monoclinic, space group $\text{P2}{}_1\text{m}$, with a = 4.977 ± 0.004, b = 6.350 ± 0.004, c = 8.160 ± 0.004 Å and β = 92°20′ ± 4′, with two formulas per unit cell; γ-Cu(IO₃)₂ becomes antiferromagnetic below Θ_N = 5 K. Cu(IO₃)₂·2H₂O is monoclinic, space group $\text{P2}{}_1\text{c}$, with a = 6.725 ± 0.005, b = 4.770 ± 0.007, c = 11.131 ± 0.013 Å and β = 103°1′ ± 4′, with two formulas per unit cell; Cu(IO₃)₂·2H₂O is paramagnetic to 1.4 K. $\text{Cu(IO}{}_3\text{)}{}_2\text{·}\text{2}\text{3}\text{H}{}_2\text{O}$ (mineral bellingerite) is triclinic, space group $\text{P}\text{1}$, with a = 7.197 ± 0.005, b = 7.824 ± 0.004, c = 7.904 ± 0.004 Å, α = 105°2′ ± 2′, β = 97°7′ ± 2′ and γ = 92°54′ ± 2′ with three formulas per unit cell; this crystal is paramagnetic to 1.4 K, with a moderate antiferromagnetic Cu-Cu interaction. Cu(OH)IO₃ (mineral salesite) is orthorhombic, with a = 10.772 ± 0.004, b = 6.702 ± 0.002 and c = 4.769 ± 0.002 Å and four formulas per unit cell. The magnetic susceptibility indicates the possibility of antiferromagnetic ordering at 162 K; strong antiferromagnetic interactions give Θ_p = ?340 K. The only copper iodate studied that generates second harmonics is α-Cu(IO₃)₂. Indexed powder patterns are given for all six compounds.     

Etude structurale d'un nouveau tellurate alcalin: Na2TeO4. Evolution de la coordination du tellure(VI) et du cation quand on passe du cation lithium au sodium

Single crystal Na₂TeO₄ has been prepared by hydrothermal synthesis and its structure determined from three dimensional X-ray analysis. The crystal is monoclinic, space group $\text{P}\text{P2}{}_1\text{c}$ with a = 10.632(5)Å, b = 5.161(2)Å; c = 13.837(11)Å, and β = 103.27(4)°. The crystal structure is built up of chains of Te(VI)O₆ octahedra parallel to the [010] axis which can be formulated as [TeO₄]_n^2n?. All sodium cations are in very distorted octahedral coordination.     

Dimorphisme et structure du disulfure de lanthane LaS2

The stoichiometric lanthanum disulfide LaS₂ presents a reversible phase transition at about 750°C. The α low-temperature form is monoclinic with the LaSe₂ type. All the crystals are twinned with the same twin law (100). The cell parameters are a = 8.18, b = 8.13, c = 4.03Å, γ = 90°, space group $\text{P2}{}_1\text{a}$. The β high-temperature form has the orthorhombic structure previously described with the parameters a = 8.13, b = 16.34, c = 4.14 Å; space group Pnma. The two structures are compared.     

The crystal structure of topotactically dehydrated copper(II) formate tetrahydrate

Thermal dehydration of copper(II) formate tetrahydrate leads to a modification of the anhydrous salt different from that produced by direct preparation of the latter. As the dehydration is a topotactic process, the known crystal structure of the tetrahydrate and the topotactic orientation relations can be used to deduce the crystal structure of the product. Single-crystal X-ray diffraction patterns of decomposed pseudomorphs yield the following unit cell for the dehydrated formate: monoclinic, a = 8.195 ? 0.006 Å, b = 7.925 ? 0.006 Å, c = 3.620 ? 0.005Å, β = 122.21 ? 0.09°, probable space group $\text{P2}{}_1\text{a}\text{= C}{}^5{}_{\mathrm{2h}}$. The structure contains copper formate layers very similar to those in the tetrahydrate, stacked in such a way that columns of distorted coordination polyhedra, linked by formate bridges, are formed. The topotactic dehydration occurs in such a way that two-dimensional elements of the structure are unaltered but the mode of stacking is changed.     

A new tungsten trioxide hydrate, WO3 · 13H2O: Preparation,characterization, and crystallographic study

A new hydrate of tungsten trioxide, $\text{WO}{}_3\text{·}\text{1}\text{3}\text{H}{}_2\text{O}$ has been obtained by hydrothermal treatment at 120°C of an aqueous suspension of either tungstic acid gel or crystallized dihydrate. This hydrate has been characterized by different methods. A crystallographic study was carried out from X-ray powder diffraction. The hydrate crystallizes in the orthorhombic system: a = 7.359(3) Å, b = 12.513(6) Å, c = 7.704(5) Å, Z = 12. The existence of structural relationships between the hydrate, $\text{WO}{}_3\text{·}\text{1}\text{3}\text{H}{}_2\text{O}$, and the product of dehydration, hexagonal WO₃, has permitted us to propose a structural model in agreement with the experimental data. $\text{WO}{}_3\text{·}\text{1}\text{3}\text{H}{}_2\text{O}$ must be regarded as an interesting compound because its dehydration leads to a new anhydrous tungsten trioxide, hexagonal WO₃.     

Phases in the Ba3Fe1+xS5 series: The structure of β-Ba9Fe4S15 and its low-temperature α polymorph

The crystal structure of β-Ba₉Fe₄S₁₅ shows that it is a phase in the infinitely adaptive series of compounds Ba₃Fe_1+xS₅, 0 ? x ? 1. The material is synthesized by reacting a slightly sulfur-rich mixture at 900°C in a sealed quartz ampoule. Lattice constants are a = 25.212(3), Å, b = 9.594(1), Å, c = 12.575(1), Å, Pnma, z = 4. Three thousand thirty-three structure amplitudes were refined to R = 0.049. BaS₆ trigonal prisms share triangular faces to form infinite columns; the columns in turn share edges and create nearly hexagonal enclosures. Within these rings are additional Ba and S and tetrahedral interstices are created which can be occupied by Fe. The variation of the Fe occupancy from ring to ring gives rise to phases in which one dimension is an integral multiple of the 8.5-Å repeat observed in one end member of the series, Ba₃FeS₅. The other end member is Ba₃Fe₂S₅. At temperatures below 900°C a polymorphic phase is formed. Its lattice constants are a = b = 9.634(1), Å, c = 34.311(3)Å, $\text{I4}{}_1\text{a}\text{, z = 4}$. One thousand five hundred eighty-three structure amplitudes were refined to R = 0.0483. Trigonal prisms and bisdisphenoids articulate to form a complex three-dimensional structure. Two of the S atoms in the structure have statistical site occupancies.     

Structure cristalline de SrFeF5

The crystal structure of SrFeF₅ has been determined by single crystal X-ray diffraction methods.The unit cell is monoclinic (space group $\text{P2}{}_1\text{c}$) with a = 7.062 ± 0.001 Å, b = 7.289 ± 0.001 Å, c = 14.704 ± 0.001 Å, β = 95.40 ± 0.01° and Z = 8.The lattice is built up of spiral chains of octahedra parallel to the Oy axis. These chains are formed by (FeF₆)^3? octahedra sharing corners of the same edge. The strontium atoms bridge three neighbouring chains. The SrTiF₅, SrVF₅, SrCoF₅, and BaInF₅ phases are isostructural with SrFeF₅.     

(Cr3AsO13)3−: Un nouveau type d'anion condensé. Préparation chimique et données cristallographiques sur (NH4)2HCr3AsO13

(NH₄)₂HCr₃AsO₁₃ is monoclinic ($\text{P2}{}_1\text{c}$) with a tetramolecular unit cell: a = 13.99(1), b = 9.47(1), c = 9.55(1) Å, and β = 93.10(1)°. We describe the chemical preparation and give crystal data for this compound.     

BeP2: A tetrahedral structure of type order-disorder which obeys a coordination rule for short-range order

Single-crystal studies on BeP₂ indicate that this compound possesses an OD structure. The substructure has a tetragonal unit cell with: a = 3.546 Å, c = 15.01 Å, Z = 4, space group: $\text{I4}{}_1\text{amd}$. The final R factor has a value of 0.033. The atom sites in this substructure correspond to the sites of diamond if the latter is described with a tetragonal cell, where $\text{a = (}\text{2}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{2}\text{)a}{}_{\mathrm{<mtext>diamond</mtext>}}$ and c = 3a_diamond. A short-range order governs the occupation of these sites with Be and P atoms. Each Be has four tetrahedral P neighbors and every P has two Be and two P neighbors. Consideration of the maxima on the diffuse streaks between the sharp reflections of the substructure leads to an intermediate unit cell with a = 7.09 Å and c = 30.02 Å. Coordination considerations allow a structure proposal to be formulated for this intermediate structure which is triclinic but pseudotetragonal. The true unit cell is also pseudotetragonal with a = 7.09 Å and c = N · 15.01 Å, where N is a large integer.     

The crystal structure of a new nonstoichiometric phase Cs1−xLu3F10−x (x ⋍ 0.25)

A high-temperature phase with the formula $\text{Cs}{}_{\mathrm{1?x}}\text{Lu}{}_3\text{F}{}_{\mathrm{10?x}}\text{(x ? 0.25)}$ has been characterized during the investigation of the CsFLuF₃ system. This phase crystallizes in the monoclinic system with unit-cell dimensions a = 13.764(5) Å, b = 7.947(1) Å, c = 4.299(2)Å, β = 90.04(5)° and space group Cm (No. 8), Z = 2. The structure was solved by conventional Patterson and Fourier methods and refined by full-matrix least-squares techniques to a conventional R of 0.053 (R_w = 0.079) for 2038 independent reflections recorded on an automatic four-circle diffractometer. The structure may be regarded as built up of (Lu₃F₁₀)^? layers that may be described as corner- and edge-shared LuF₇ pentagonal bipyramids. These layers run parallel to the (001) plane. The structure extends along the third direction by cornersharing involving axial vertices of the pentagonal bipyramids. This three-dimensional framework delimits tunnels running parallel to the c direction where the Cs⁺ ions lie. The partial occupancies of both the Cs site and one out of the seven independent fluorine sites results in the nonstoichiometry.     

Synthesis and structure of an infinite-chain form of ZrI2 (α)

The synthesis of a second polymorph of ZrI₂ has been achieved by a transport reaction between ZrI₄ and zirconium metal under a $\text{750}\text{850}\text{°}\text{C}$ gradient in a sealed tantalum tube. The black lath-like crystals produced in the 775°C region occur in space group $\text{P2}{}_1\text{m}$ with a = 6.821(2) Å, b = 3.741(1) Å, c = 14.937(3) Å, β = 95.66(3)°, Z = 4. A total of 669 independent reflections with 2θ ≤ 50° and I > 3σ(I) were measured at room temperature on a four-circle automated diffractometer with monochromatized MoKα radiation and were corrected for absorption (μ = 190 cm^?1). The structure was solved by direct methods and full-matrix least-squares refinement of all atoms with anisotropic thermal parameters to give final residuals R = 0.064 and R_w = 0.079. This phase is isoelectronic and isostructural with β-MoTe₂, a distorted CdI₂-type structure in which the zirconium atoms are displaced 0.440 Å from the octahedral centers along a to form infinite zigzag metal chains (d_ZrZr = 3.182(3) Å) parallel to b. The phase is a diamagnetic semiconductor at room temperature (E_g ～ 0.1 eV).     

Neutron powder profile studies of the gamma uranium trioxide phases

Neutron powder profile studies show the existence of three phases in gamma uranium trioxide between 373°K and 77°K. The three phases are closely related and the transitions smooth and displacive. At 373°K, γ-UO₃ is tetragonal, with a = 6.9013 (5) and c = 19.9754 (18) Å, and space group $\text{I4}{}_1\text{amd(}\text{D}{}^{19}{}_{\mathrm{4h}}\text{)}$. At 323°K, γ-UO₃ becomes orthorhombic, space group F_ddd(D²⁴_2h), with the cell dimensions (293°K) a = 9.787 (3), b = 19.932 (4) and c = 9.705 (3) Å. There is a further transition between 293°K and 77°K, and, at 77°K, the orthorhombic dimensions of the pseudocell are a = 9.8225 (7), b = 19.8487 (15), and c = 9.6318 (7) Å. The neutron diffraction studies show that, in all three phases, the coordination polyhedra of the two crystallographically distinct uranium atoms are octahedral and (dodecahedral-2) respectively. At 293°K, the shortest UO distance is 1.796 (6) Å, and thus there are no pure uranyl bonds, in agreement with the infrared spectrum. The UO distances are precise to about ± 0.006 Å, about ten times the precision of an earlier X-ray single-crystal study, in which the conclusions were in conflict with the infrared spectrum. The structure is made up of parallel chains of edge-fused U(2) octahedra, cross-linked by U(1) dodecahedra. The atomic shifts are not great in going from 373°K to 77°K; at 293°K the data will refine in the pseudotetragonal cell as well as the true orthorhombic cell, and the 77°K data will refine in the F_ddd cell.