Crystal structure of KSbP2O8

KSbP₂O₈ crystallizes in the rhombohedral system, space group $\text{R}\text{3}$, with a = 4.7623(4) Å, c = 25.409(4)Å, and Z = 3. The structure was determined from 487 reflexions collected on a NONIUS CAD4 automatic diffractometer with MoK^?α radiation. The final R index and weighted R_w index are 0.030 and 0.038, respectively. This structure is built up from layers of SbO₆ octahedra and PO₄ tetrahedra sharing corners. These (SbP₂O^?₈)_n layers are very similar to the (ZrP₂O^2?₈)_n layers in the well-known α-ZrP compound.     

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.     

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.     

A structural model for barium platinum oxide,Ba3Pt2O7

A single crystal study of Ba₃Pt₂O₇ shows that the structure tolerates a variable composition which can be written Ba₃Pt_2+xO_7+2x. The crystal studied has a hexagonal cell of dimensions a = 10.108 ± 0.006 Å and c = 8.638 ± 0.009 Å, and a probable space group $\text{P}\text{6}\text{2c, Z = 4}$. The density determined by water displacement is 7.99 g/cm³; the theoretical density for Ba₃Pt₂O₇ is 7.94 g/cm³. The structure was determined from the set of 401 observed independent reflections obtained from 5189 reflections measured by automated counter methods. Refinement on F was carried to a conventional R of 8.0%. The structure has barium-oxygen layers with an essentially four-layer stacking sequence of the double hexagonal (ABAB) type. Platinum is found mainly in face-sharing octahedra, but is also distributed over some sites in which the coordination is nearly square planar and other sites in which the coordination is trigonal prismatic with three PtO bond lengths of 2.00 Å and three long PtO distances of 2.65 Å. The platinum with planar coordination is 0.08 Å from the plane of the four oxygen atoms.     

The crystal structure of the 2:5 phase in the K2OZrO2 system: K4Zr5O12, a compound with octahedral and trigonal prismatic zirconium(IV) coordination

K₄Zr₅O₁₂ crystallizes in the trigonal system with unit-cell dimensions a = 5.821(2) Å, c = 10.437(3) Å, and space group $\text{P}\text{3}\text{m1}$. The structure was solved by Patterson and Fourier techniques. the 386 unique reflections measured by counter techniques were reduced to 334 with I ? 3σ (I); these were used in full-matrix least-squares refinement of the model to a conventional R of 0.0196 (ωR = 0.0228). K₄Zr₅O₁₂ has a structure that may be described as consisting of perovskite-like layers (potassium ions are cube octahedrally coordinated) with sheets of hexagonal rings of edge-shared trigonal prismatically coordinated zirconium(IV) ions inserted between every third and fourth layer of the perovskite-like structure. The trigonal prisms are face shared to octahedra above and below alternately to form cavities that are occupied by pairs of potassium ions in ninefold coordination.     

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.     

A pentagonal tunnel structure with copper in square planar coordination: The oxides KCuNb3O9 and KCuTa3O9

The structure of two new oxides KCuTa₃O₉ and KCuNb₃O₉ has been solved from X-ray powder data and by electron microscopy. Both compounds are orthorhombic, space group Pnc2 with $\text{a ? 8.8}$ Å, $\text{b ? 10.1}$ Å, and $\text{c ? 7.6}$ Å. Their host lattice is built up from corner-sharing MO₆ octahedra (M = Nb, Ta) forming pentagonal tunnels where the K⁺ ions are located. The copper ions are located in distorted perovskite CaCu₃Mn₄O₁₂-type cages and exhibit a square planar coordination. The relationships between these oxides and the TTB, HTB, ITB, and Ba_0.15WO₃ structures are discussed.     

La3Os2O10, a new compound containing isolated clusters Os2O10 with metal-metal bonds

The formula of a new compound isolated in the LaOsO system has been established by means of crystal structure determination. There are two La₃Os₂O₁₀ units in a face-centered monoclinic unit cell (S.G. $\text{C2}\text{m}$); a = 7.911(2) Å, b = 7.963(2) Å, c = 6.966(2)Å, β = 115.76(2)°;. For 1082 intensities, collected on an automated single-crystal diffractometer, the final R value was 0.025 after absorption corrections. The structure consists of isolated Os₂O₁₀ clusters composed of two edge-shared OsO₆ octahedra. These dimeric units are connected together by two types of La³⁺ ions in eightfold coordination. In view of the OsOs distance inside the pair (2.462 Å), La₃Os₂O₁₀ provides an example of metal-metal bonding involving a transition metal in a half-integral formal oxidation state of 5.5.     

The crystal structure and some properties of Eu2Sb3

The Mooser-Pearson phase Eu₂Sb₃ crystallizes in a new monoclinic structure type, space group $\text{P2}{}_1\text{c}$ (No. 14) with a = 6.570(1) Å, b = 12.760(2) Å, c = 15.028(2) Å, β = 90.04(1)°; Z = 8. The Sb atoms form six-membered twisted chain fragments oriented along the b-axis. The Eu atoms are eight- and nine-coordinated by Sb. The Eu₂Sb₃ structure is closely related to the structure of Ca₂As₃. The relations between their space-group symmetries are derived and hypothetical higher-symmetry structures are discussed. The semiconducting Eu₂Sb₃ is antiferromagnetic below T_N = 14.4°K. An Eu₂Sb₃-type structure was found also for Sr₂Sb₃.     

Refinements of the six-layer structures of the R-type hexagonal ferrites BaTi2Fe4O11 and BaSn2Fe4O11

The structures of BaTi₂Fe₄O₁₁ and BaSn₂Fe₄O₁₁ have been determined from neutron powder diffraction data collected at 300 K using the Rietveld profile refinement. The compounds were found to be isostructural, space group $\text{P6}{}_3\text{mmc}$. BaTi₂Fe₄O₁₁: a = 5.8470(2) Å, c = 13.6116(9) Å, V = 403.01(5) ų, M = 632.6, Z = 2, D_calc. = 3.09 Mg m^?3, final R-factor = 3.77. BaSn₂Fe₄O₁₁: a = 5.9624(5) Å, c = 13.7468(14) Å, V = 423.23(10) ų, M = 774.2, Z = 2. D_calc. = 3.66 Mg m^?3, final R-factor = 2.41. The structure consists of h-stacked BaO₃ and O₄ layers in the ratio 1:2. The BaO₃ layers contain a mirror plane. Between the O₄ layers three octahedral sites are occupied, and between the BaO₃ and O₄ layers an octahedral site and a tetrahedral site are occupied. Because of the mirror plane in the BaO₃ plane the latter sites both share faces in the BaO₃ plane. The octahedral sites are occupied by Fe and Ti or Sn, the pair of tetrahedral sites is occupied by one Fe atom. This Fe atom may hop between these two tetrahedral sites. The structure is considered to be constructed by two R-blocks of the BaFe₁₂O₁₉ (M) structure. Unit-cell dimensions are given of a number of isostructural compounds of general formula A^IIB^IV₂C^III₃O₁₁. Mössbauer experiments on some of these compounds were focused on the tetrahedral positions that show an unusual quadrupole splitting. A brief review is given of the observed magnetic properties of some compounds with the R-structure.     

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.     

Oxysulfure de scandium Sc2O2S

Sc₂O₂S is hexagonal, $\text{P6}{}_3\text{mmc}\text{, a = 3.5196(4)}$ Å, c = 12.519(2) Å, Z = 2, Dc = 3.807 g cm^?3, Dm = 4.014 g cm^?3, μ(MoKα) = 55.51 cm^?1. The final R value is 0.038 for 205 symmetry-independent reflections. This scandium oxysulfide has c = 12.52 Å, twice the value found in rare earth oxysulfides. An La₂O₂S cell combined with its reflection in a (001) mirror gives the Sc₂O₂S cell.     

Structure of the copper(I) tantalum oxide,Cu5Ta11O30

The structure of hexagonal Cu₅Ta₁₁O₃₀ (space group $\text{P}\text{6}\text{2c}$) has been determined from single-crystal diffractometer data. The cell dimensions are a = 6.2297(2) Å and c = 32.550(2) Å, and the cell content is two formula units. The structure is related to those of CaTa₄O₁₁ and CeTa₇O₁₉ and contains alternately single and double layers of TaO₇ pentagonal bipyramids sharing edges in the equatorial plane in the same way as UO₇ in α-U₃O₈. The layers are connected by TaO₆ octahedra and linear CuO₂ groups, both formed by the apex oxygens of the TaO₇ bipyramids. Refinement was made with the least-squares technique using 729 reflections, of which 422 were independent. The conventional R value was 3.9%.     

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.     

Bronzes with a tunnel structure KxP4O8(WO3)2m: The tenth member of the series—KP8W40O136

The crystal structure of KP₈W₄₀O₁₃₆, the tenth member of the series K_xP₄O₈(WO₃)_2m, has been resolved by three-dimensional single-crystal X-ray analysis. The space group is $\text{P2}{}_1\text{c}$ and the cell parameters are a = 19.589(3) Å, b = 7.5362(4) Å, c = 16.970(3) Å and β = 91.864(14)°. The framework is built up from ReO₃-type slabs connected through pyrophosphate groups. The structure is compared to those of the other members of the series: although the ReO₃-type slabs show a different type of tilting of the WO₆ octahedra, the dispersion of WO distances is always higher for the octahedra linked to one or two P₂O₇ groups and decreases in proportion as W is farther from these groups. The perovskite cages of the slabs are described and compared to those encountered in the structures of WO₃ and of the bronzes A_xWO₃.     

The pyrophosphate NaFeP2O7: A cage structure

The high-temperature form of NaFeP₂O₇ crystallizes in the monoclinic $\text{P2}{}_1\text{c}$ space group with a = 7.3244(13), b = 7.9045(7), c = 9.5745(15), Å, β = 111.858(13)°, and Z = 4. The structure has been refined from 3842 reflections leading to R = 0.040 and R_w = 0.047. The structure of II-NaFeP₂O₇ can be described by alternately stacking layers containing the FeO₆ octahedra and layers formed by the P₂O₇ groups, parallel to (001). Elongated cages are formed where two Na⁺ ions are located. The structure is compared with that of KAlP₂O₇. Both structures are built up from blocks of three polyhedra, [FeP₂O₁₁] or [AlP₂O₁₁], including a small O_octO_tetO_oct angle. These blocks are connected in such a way that several types of tunnels appear in each structure.     

Crystal structures of some niobium and tantalum oxides. VIII. The 5Rb2O:14.6Ta2O5 phase—A tunnel structure

Rb₁₀Ta_29.20O₇₈ crystallizes in the hexagonal system with unit-cell dimensions (from single-crystal data) a = 7.503(4)Å, c = 36.348(4)Å, and space group $\text{P6}{}_3\text{mmc}\text{, z = 1}$. The structure was solved using three-dimensional Patterson and Fourier techniques. Of the 666 unique reflections measured by counter techniques, 515 with I ? 3σ(I) were used in the least-squares refinement of the model to a conventional R of 0.057 (R_ω = 0.039). The structure of Rb₁₀Ta_29.20O₇₈ consists of layers of corner-sharing groups of six edge-shared octahedra separated by layers of single octahedra and double hexagonal tungsten bronze-like layers, these layers being perpendicular to the hexagonal c-axis. Nine-coordinate tricapped trigonal prismatic sites between the hexagonal tungsten bronze-like layers are partially occupied by Ta(V) ions.     

KxP2W2O16: A bronze with a tunnel structure built up from PO4 tetrahedra and WO6 octahedra

The structure of a $\text{K}{}_{\mathrm{x}}\text{P}{}_2\text{W}{}_4\text{O}{}_{16}\text{(x ? 0.4)}$ crystal was established by X-ray analysis. The solution in the cell of symmetry $\text{P2}{}_1\text{m}$, with a = 6.6702(5), b = 5.3228(8), c = 8.9091(8) Å, β = 100.546(7)°, Z = 1, has led to R = 0.033 and R_w = 0.036 for 2155 reflections with $\text{σ(I)}\text{I}\text{≤ 0.333}$. This structure can be described as two octahedra-wide ReO₃-type slabs connected through “planes” of PO₄ tetrahedra. A new structural family K_xP₂W_2nO_6n+4 can be foreseen which is closely related to the orthorhombic P₄W₈O₃₂ and the monoclinic Rb_xP₈W_8nO_24n+16 series.     

Crystal chemistry of the BaNbS system: A layer structure of approximate composition Ba2NbS4(S2)0.5

Black platy crystals from the product of a reaction mixture of 6BaS : 3Nb : 7S reacted at 1000°C were hexagonal with a = 6.909(4) Å, c = 49.25(2) Å, $\text{P6}{}_3\text{mmc}\text{, Z = 10}$. A pronounced subcell with a = 6.91Å, c = 5.5 Å indicated that this was a layer structure consisting of stacking of close-packed BaS₃ layers. Three dimensional X-ray diffraction data were collected from a single crystal using monochromatized MoKα radiation. From the 1535 measured reflections, 782 unique structure amplitudes were obtained of which 608 greater than 2σ(F) were used to solve the structure. The final R = 0.1065, ωR = 0.0793; for 91 reflections with l = 9n, R = 0.0397 and for the 517 reflections l ≠ 9n, R = 0.138. The structure is based on the stacking of close-packed BaS₃ layers with the sequence CBDBABDBC BCDCACDCB, where D designates a disordered layer. The disordered layers contain two crystallographically independent Ba with partial site occupancies and disordered S₂ and S ions. Nb occupy octahedral interstices and form two different arrangements; a unit consisting of 3 face-sharing octahedra and a unit of 2 face-sharing octahedra. These octahedral units are separated by the disordered layers. The NbNb distances in the chain of 3 are 3.29 Å and they are 3.57 Å in the double unit.     

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.