The crystal structure of the 42-Å subcell of a layer structure with approximate composition Ba4Nb2S9

Platy crystals from the products of a mixture 4 Bas : 2 Nb : 5 S reacted at 1000°C have cell constants a = 13.754(3) Å, c = 83.73(2) Å, $\text{R}\text{3}\text{m}$. The reciprocal lattice had a pronounced subcell with dimensions a = 6.877(1) Å, c = 41.84(1) Å, same space group. Three dimensional X-ray diffraction data were collected using monochromatized Mo Kα radiation and of 5051 measured intensities 1892 were considered observed. From the set of observed intensities 611 reflections having all even indices were used to refine the crystal structure of the 42 × 7-Å subcell. The final R = 0.036 and ωR = 0.052 for the 611 observed amplitudes and R = 0.046, ωR = 0.052 for all 711 amplitudes of the subcell. The structure is based on the stacking of hexagonal BaS₃ layers with the sequence DABABDBCBCDCACAD. The D layer denotes a disordered level and occurs at $\text{z = 0,}\text{1}\text{3}$ and $\text{2}\text{3}$. The different letters for the ordered layers are based on the Ba positions in that layer. The Nb ions occupy octahedral interstices and form a unit of three face sharing octahedra parallel to c. The column is terminated above and below by disordered levels. The NbNb distances are 3.22 Å, causing displacement of Nb from the centers of the two outside octahedra. One Ba is in the center of a triangular orthobicupola formed by 12 S atoms. The other Ba is in the center of a hexagon of 6 S with 3 additional S above this layer forming $\text{1}\text{2}$ of a cuboctahedron. The lower half consists of a disordered layer of atoms. The NbS distances are 2.279, 2.433, and 2.683 Å; BaS distances vary between 3.1 and 3.5 Å. The subcell content based on the ordered structure only is Ba₁₂Nb₉S₃₆. The placement of disordered Ba and S at $\text{z = 0,}\text{1}\text{3}$, and $\text{2}\text{3}$ levels of the subcell leads to the unlikely composition Ba_16.5Nb₉S₄₂. The ordered structure most likely has a composition Ba₄Nb₂S₉, z = 36, so that the subcell composition should be Ba₁₈Nb₉S_40.5. The completely ordered structure has not been solved.     

Neutron diffraction determination of the crystal structure of Ce7O12

A neutron diffraction study has been made on polycrystalline and single crystal samples of CeO_1.714. The results confirm that the compound is isostructural with ternary oxides of the type UY₆O₁₂. The space group is $\text{R}\text{3}$ with hexagonal unit cell dimensions a = 10.37 Å and c = 9.67 Å (rhombohedral cell a = 8.60 Å and α = 99.4°). The hexagonal unit cell contains three formula units of Ce₇O₁₂. Totals of 79 and 24 independent reflections from the single crystal were measured at neutron wavelengths of 1.185 and 2.37 Å, respectively. Simultaneous refinement of the two sets of data yielded a weighted R factor of 0.144. The structure is a rhombohedral defect type of fluorite arrangement in which pairs of oxygen vacancies are ordered along the [111] axis.     

The crystal structure of α-SrMnO3

α-SrMnO₃ crystallizes in the hexagonal system with unit-cell dimensions a = 5.454(1) Å, c = 9.092(2)Å, space group $\text{P6}{}_3\text{mmc}\text{, Z = 4}$. The structure was solved by the heavy-atom method; of 404 unique reflections measured by counter method, 203 that obeyed the condition |F₀| ≥ 3σ (|F₀|) were used in the refinement to a conventional R value of 0.043. The structure consists of four close-packed SrO₃ layers in an ABAC stacking sequence along the hexagonal c axis. Oxygen octahedra containing Mn⁴⁺ are grouped into face-sharing pairs linked by corner sharing within the cubically stacked “A” layer.     

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.     

Neutron powder diffraction and magnetic measurements on CsMnI3

Results of neutron powder diffraction and magnetic measurements on single crystals of CsMnI₃ are reported. Three-dimensional ordering takes place at T_c = 11.1(3) K. Above T_c very broad peaks occur in the neutron powder diffraction diagram, indicating one-dimensional correlations along the chain. Below T_c the Mn²⁺ ions are coupled antiferromagnetically along the chain. Interchain exchange leads to a 120° structure, slightly distorted due to anisotropy. One-third of the chains have their magnetic moment parallel to the c axis and the rest of the chains have magnetic moments making an angle of 50(2)° with the c axis. The magnetic moment as found from neutron diffraction extrapolated to 0 K is 3.7(1)μ_B, indicating a considerable zero-point spin reduction. The intrachain exchange $\text{J}\text{k}$ was found to be ?9.1(1)K, whereas the ratio of the inter- to intrachain interaction was determined as $\text{J′}\text{J}\text{= × 10}{}^{\mathrm{?3}}$. A spin flop occurs at H = 54 kOe on application of a magnetic field parallel to the c axis. When a field perpendicular to the c axis is applied a spin reorientation occurs at 1 kOe.     

A cationic dicarbene complex of iron. The crystal structure of [Fe(CO)2(S2CNMe2)(CNMe2)2S]PF6 · 12C2H4Cl2

The structure of the compound [Fe(CO)₂(S₂CNMe₂)(CNMe₂)₂S]PF₆ · $\text{1}\text{2}$C₂H₄Cl₂ has been determined by X-ray crystallography. The compound crystallizes in space group C2/c with eight formula units in a unit cell of dimensions a 23.939(18), b 15.771(7), c 12.314(4) Å, β 92.01(5)°. Full-matrix least-squares refinement of 2084 counter data yielded R = 0.051. The complex cation contains an unusual chelating dicarbene ligand, and the structure of this complex is compared with related species. The bonding properties of the dicarbene ligand are discussed.     

The structure of the fluorite-related phase Ca2Hf7O16

The atomic arrangement in the fluorite-related phase, Ca₂Hf₇O₁₆, has been determined by powder X-ray diffraction. The unit cell is rhombohedral, $\text{R}\text{3}$, with a = 9.5273Å, α = 38.801°, and Z = 1, and its volume is $\text{2}\text{1}\text{4}$ times that of the fluorite subcell from which it is derived. The cations are ordered on the cation sites of the fluorite structure with the calcium ions segregated into discrete layers parallel to the (111) fluorite plane: there is some evidence that the formal anion vacancies are also ordered.     

Idle spin behavior of the shifted hexagonal tungsten bronze type compounds FeIIFeIII2F8(H2O)2 and MnFe2F8(H2O)2

Fe^IIFe^III₂F₈(H₂O)₂ and MnFe₂F₈(H₂O)₂, grown by hydrothermal synthesis ($\text{P ? 200}\text{MPa}\text{, T = 450}\text{or}\text{380°}\text{C}$), crystallize in the monoclinic system with cell dimensions (Å): a = 7.609(5), b = 7.514(6), c = 7.453(4), β = 118.21(3)°; and a = 7.589(6), b = 7.503(8), c = 7.449(5), β = 118.06(3)°, and space group $\text{C2}\text{m}\text{, Z = 2}$. The structure is related to that of $\text{WO}{}_3\text{·}\text{1}\text{3}\text{H}{}_2\text{O}$. It is described in terms of perovskite type layers of Fe³⁺ octahedra separated by Fe²⁺ or Mn²⁺ octahedra, or in terms of shifted hexagonal bronze type layers. Both compounds present a weak ferromagnetism below T_N (157 and 156 K, respectively). Mössbauer spectroscopy points to an “idle spin” behavior for Fe^IIFe^III₂F₈(H₂O)₂: only Fe³⁺ spins order at T_N, while the Fe²⁺ spins remain paramagnetic between 157 and 35 K. Below 35 K, the hyperfine magnetic field at the Fe²⁺ nuclei is very weak: H_hf = 47 kOe at T = 4.2 K. For MnFe₂F₈(H₂O)₂, Mn²⁺ spin disorder is expected at 4.2 K. This “idle spin” behavior is due to magnetic frustration.     

Monoclinic-trigonal transition in some MI3M′III(XO4)3 compounds: The high temperature form of (NH4)3In(SO4)3

The high-temperature form of (NH₄)₃In(SO₄)₃ is rhombohedral, R3c, with a = 15.531 (12), c = 9.163 (8)Å, Z = 6. The structure was solved to R = 0.023 for 570 independent reflections measured at about 140°C. The structure is built up of [In(SO₄)₃]_∞ columns extending along the c axis and composed of InO₆ octahedra and SO₄ tetrahedra linked together; this arrangement is very similar to that found in the low-temperature form. To explain the transition mechanism, the existence of an intermediate phase of point symmetry $\text{3}$ is postulated and the whole sequence of possible forms would be $\text{2}\text{m}\text{→}\text{3}\text{→ 3m →}\text{3}\text{m}$. This last phase would be the prototypic structure of the possibly ferroelastic low-temperature modification, which can apparently exist only with nonspherical monovalent cations.     

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.     

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.     

Neutron powder diffraction on α-Tl4CrI6 and β-Tl4CrI6

α-Tl₄CrI₆ (a = 9.132(1), c = 9.667(1) Å, $\text{Z = 2,}\text{P4}\text{mnc}$ at 293 K) adopts a distorted Tl₄HgBr₆ structure. In α-Tl₄CrI₆ there occurs a random distribution of Jahn-Teller distorted octahedra which are elongated perpendicular to the c axis. Between 77 and 4.2 K a phase transition occurs. In β-Tl₄CrI₆ (a = 12.941(3), b = 12.596(3), c = 9.602(2) Å, Z = 4, Cccm at 4.2 K) the directions of elongation of the octahedra are ordered. The structure is very much related to that of α-Tl₄CrI₆. A three-dimensional magnetic ordering takes place at 2.7(2) K. The magnetic space group at 1.2 K is C_I22′2′. The magnetic moments (3.48(6) μ_B) are parallel to (0 0 1) and have an angle of 41(9)° with the a axis. Four magnetic sublattices are present, forming two independent magnetic lattices which have no interaction due to the antiparallel ordering.     

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.     

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;.     

Growth and physical properties of single crystals of FeII2MoIV3O8

Crystals of hexagonal Fe₂Mo₃O₈ up to 3 × 3 × 2 mm were grown by chemical vapor transport from a starting mixture of composition Fe₂MoO₄. The morphology is {101}, {$\text{10}\text{2}$}, {110}, {$\text{00}\text{2}$}, {100} and corresponds to the absolute orientation of the polar z axis. Both magnetic susceptibility and electrical conductivity show considerable anisotropy. The compound orders antiferromagnetically at 59.5 K, with the spin along c. It is a low-conductivity semiconductor with activation energies 0.14 and 0.21 eV perpendicular and parallel to c, respectively.     

Reaction of some tertiary phosphines and phosphites with [Co(η5-C5H5)(S2C2{CN}2)]

Reaction of the 16 electron monomer [Co(η⁵-C₅H₅)(S₂C₂{CN}₂)] with various tertiary phosphines and phosphites (L) gives readily the 18 electron monomers [Co(η⁵-C₅H₅)(S₂C₂{CN}₂)L] which for L = P(OR)₃ have J($\text{P}$C₅$\text{H}$₅) ca. 6 Hz but J($\text{P}$C₅$\text{H}$₅) = 0 for L = PR₃.     

Etude structurale des sulfotellurures de terres rares (LS)2Te1 + x (L = Tb,Dy, Ho,Er, Tm et Y). II. Surstructure des phases ordonnées. Macles d'ordre

The (LS)₂Te_{1 + x} compounds have an orthorhombic subcell, with a layered structure and vacant Te sites, and a monoclinic superstructure (a = b = 6.658, c = 13.657 Å, γ = 102°43′ for (HoS)₂Te_1.34). The order-disorder transition occurs at about 450°C. In the superstructure Te planes between (L₄S) tetrahedra layers are ordered with $\text{B2}\text{m}$ symmetry; however, some sites remain partially vacant. The S atoms conserve mmm symmetry, but the metallic atoms are slightly displaced from their substructure position (R = 0.037). Ordering occurs so that each Te plane can be oriented in two different ways. Therefore, there are two kinds of domains, with respect to a twinning rule. These domains are observed by direct-imaging high-resolution electronic microscopy and are about 100 Å wide.     

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°.     

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.     

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.