Synthesis, structure, and magnetic properties of Ba2Cu2US5

The alkaline-earth uranium chalcogenide Ba₂Cu₂US₅ was obtained in a two-step reaction from BaS, Cu₂S, and US₂. Ba₂Cu₂US₅ crystallizes in a new structure type in space group C2/m of the monoclinic system with two formula units in a cell of dimensions a=13.606(3) Å, b=4.0825(8) Å, c=9.3217(19) Å, and β=116.32(3)° (153 K). The structure consists of layers separated by Ba atoms in bicapped trigonal-prismatic coordination. The two-dimensional layer is built from US₆ octahedra and CuS₄ tetrahedra. The connectivity of the MS_n polyhedra within the layer in the [001] direction is oct tet tet oct tet tet. A μ_eff value of 2.69(2) μ_B/U was obtained from the magnetic susceptibility data. No magnetic transition was observed for Ba₂Cu₂US₅ down to 2 K.     

RbAuUSe3, CsAuUSe3, RbAuUTe3, and CsAuUTe3: Syntheses and structure; magnetic properties of RbAuUSe3

The compounds RbAuUSe₃, CsAuUSe₃, and RbAuUTe₃ were synthesized at 1073 K from the reactions of U, Au, Q, and A₂Q₃ (A=Rb or Cs; Q=Se or Te). The compound CsAuUTe₃ was synthesized at 1173 K from the reaction of U, Au, Te, and CsCl as a flux. These isostructural compounds crystallize in the KCuZrS₃ structure type in space group Cmcm of the orthorhombic system. The structure consists of layers that contain nearly regular UQ₆ octahedra and distorted AuQ₄ tetrahedra. The infinite layers are separated by bicapped trigonal prismatic A cations. The magnetic behavior of RbAuUSe₃ deviates significantly from Curie–Weiss behavior at low temperatures. For T>200 K, the values of the Curie constant C and the Weiss constant θ_p are 1.82(9) emu K mol⁻¹ and −3.5(2)×10² K, respectively. The effective magnetic moment μ_eff is 3.81(9) μ_B. Formal oxidation states of A/Au/U/Q may be assigned as +1/+1/+4/−2, respectively.     

Syntheses, structures, optical properties, and theoretical calculations of Cs2Bi2ZnS5, Cs2Bi2CdS5, and Cs2Bi2MnS5

Three new compounds, Cs₂Bi₂ZnS₅, Cs₂Bi₂CdS₅, and Cs₂Bi₂MnS₅, have been synthesized from the respective elements and a reactive flux Cs₂S₃ at 973 K. The compounds are isostructural and crystallize in a new structure type in space group Pnma of the orthorhombic system with four formula units in cells of dimensions at 153 K of a=15.763(3), b=4.0965(9), c=18.197(4) Å, V=1175.0(4) Å³ for Cs₂Bi₂ZnS₅; a=15.817(2), b=4.1782(6), c=18.473(3)  Å, V=1220.8(3)  ų for Cs₂Bi₂CdS₅; and a=15.830(2), b=4.1515(5), c=18.372(2) Å, V=1207.4(2) Å³ for Cs₂Bi₂MnS₅. The structure is composed of two-dimensional _∞²[Bi₂MS₅²⁻] (M=Zn, Cd, Mn) layers that stack perpendicular to the [100] axis and are separated by Cs⁺ cations. The layers consist of edge-sharing _∞¹[Bi₂S₆⁶⁻] and _∞¹[MS₃⁴⁻] chains built from BiS₆ octahedral and MS₄ tetrahedral units. Two crystallographically unique Cs atoms are coordinated to S atoms in octahedral and monocapped trigonal prismatic environments. The structure of Cs₂Bi₂MS₅, is related to that of Na₂ZrCu₂S₄ and those of the AMM′Q₃ materials (A=alkali metal, M=rare-earth or Group 4 element, M′= Group 11 or 12 element, Q=chalcogen). First-principles theoretical calculations indicate that Cs₂Bi₂ZnS₅ and Cs₂Bi₂CdS₅ are semiconductors with indirect band gaps of 1.85 and 1.75 eV, respectively. The experimental band gap for Cs₂Bi₂CdS₅ is ≈1.7 eV, as derived from its optical absorption spectrum.     

Synthesis, crystal structure, and electronic structure of RbVSe2

RbVSe₂ has been synthesized at 773 K through the reaction of V and Se with a Rb₂Se₃ reactive flux. The compound crystallizes in the orthorhombic space group D_2h²⁴-Fddd with 16 formula units in a cell of dimensions , , and at . The structure possesses infinite one-dimensional chains of edge-sharing VSe₄ tetrahedra separated from the Rb⁺ ions. These chains distort slightly to chains. The V-V distance within these chains is 2.8362(4) Å. First-principles total energy calculations indicate that a non-magnetic configuration for the V³⁺ cations is the most stable.     

Single crystal structure and magnetic properties of MnSbS2Cl

The new compound MnSbS₂Cl was synthesised from a mixture of MnS, MnCl₂ and Sb₂S₃ at 500 °C. Single crystal study indicates orthorhombic symmetry, space group Pnma (No. 62), with , , , and Z=4. The refinement converged to R=0.0374 and wR=0.0716 for 742 unique reflections and 32 parameters. The crystal structure of MnSbS₂Cl is isotypic with stibnite Sb₂S₃ and consists of waved layers of corner-sharing MnS₄Cl₂ octahedra along the a axis and edge-sharing octahedra along the b axis, which are separated by antimony atoms. MnSbS₂Cl susceptibility shows an antiferromagnetic behaviour below 40 K with an increase at about 23 K.     

Syntheses and structures of CsHo3Te5 and Cs3Tm11Te18 and the electronic structure of CsHo3Te5

Single crystals of CsHo₃Te₅ and Cs₃Tm₁₁Te₁₈ have been grown as byproducts in the synthesis of CsLnZnTe₃ (Ln=Ho or Tm) through the reaction of Ln, Zn, and Te with a CsCl flux at 850 °C. The crystal structures have been determined from single-crystal X-ray diffraction data. CsHo₃Te₅ crystallizes in space group Pnma of the orthorhombic system whereas Cs₃Tm₁₁Te₁₈ crystallizes in the space group C2/m of the monoclinic system. Each of the compounds adopts a three-dimensional structure; each possesses tunnels built from LnTe₆ octahedra that are filled with Cs atoms. The pseudo-rectangular tunnel in CsHo₃Te₅ is large enough in cross-section to accommodate two symmetrically equivalent Cs atoms. In the Cs₃Tm₁₁Te₁₈ structure there are two different sized tunnels: the smaller one is only large enough to host one Cs atom per unit cell whereas the larger one can accommodate two Cs atoms. The electronic structure of CsHo₃Te₅ was calculated. The band gap is estimated to be about 1.2 eV, consistent with the black color of the crystals.     

Syntheses, structures, and magnetic and optical properties of the compounds [Hg3Te2][UCl6] and [Hg4As2][UCl6]

Two new quaternary salts, [Hg₃Te₂][UCl₆] and [Hg₄As₂][UCl₆], have been synthesized and their structures determined by single-crystal X-ray diffraction analysis. [Hg₃Te₂][UCl₆] is the product of a reaction involving UCl₄, HgCl₂, and HgTe at 873 K. The compound crystallizes in space group P2₁/c of the monoclinic system. [Hg₄As₂][UCl₆] results from the reaction of U, Hg₂Cl₂, and As at 788 K. It crystallizes in space group Pbca of the orthorhombic system. [Hg₃Te₂][UCl₆] has a two-dimensional framework of layers, whereas [Hg₄As₂][UCl₆] has a three-dimensional framework of layers interconnected by Hg atoms linearly bonded to As atoms. Both framework structures contain discrete [UCl₆]²⁻ anions between the layers. [Hg₃Te₂][UCl₆] exhibits temperature-independent paramagnetism. The optical absorption spectra of these compounds display f-f transitions.     

Crystal structure and magnetic properties of Sr4Mn2NiO9

The crystal structure of Sr₄Mn₂NiO₉ has been refined on single crystal. This phase belongs to the series A_1+x(A^′_xB_1–x)O₃ (x=1/3) related to the 2H-hexagonal perovskite. The structure contains transition metals in chains of oxide polyhedra (trigonal prisms and octahedra); neighboring chains are separated from each other by the Sr atoms. The sequence of the face sharing polyhedra along the chains is two octahedra + one trigonal prism. Mn occupies the octahedra and Ni is disordered in the trigonal prism with ≈80% in the pseudo square faces of the prism and ≈20% at the centre. This result has been confirmed by XANES experiments at Mn K and Ni K edges, respectively. Sr₄Mn₂NiO₉ is antiferromagnetic with a Néel temperature at T=3 K. The Curie constant measured at high temperature is in good agreement with ≈80% of the Ni²⁺ ions in the spin state configuration S=0.     

Synthesis, structure, and electronic structure of K2CuSbS3

The new compound K₂CuSbS₃ has been synthesized by the reaction of K₂S, Cu, Sb, and S at 823 K. The compound crystallizes in the Na₂CuSbS₃ structure type with four formula units in space group P2₁/c of the monoclinic system in a cell at 153 K of a=6.2712 (6) Å, b=17.947 (2) Å, c=7.4901 (8) Å, β=120.573 (1)°, and V=725.81 (12) Å³. The structure contains two-dimensional layers separated by K atoms. Each layer is built from CuS₃ and SbS₃ units. Each Cu atom is pyramidally coordinated to three S atoms with the Cu atom about 0.4 Å above the plane of the S atoms. Each Sb atom is similarly coordinated to three S atoms but is about 1.1 Å above its S₃ plane. First-principles calculations indicate an indirect band gap of 1.9 eV. These calculations also indicate that there is a bonding interaction between the Cu and Sb atoms. An optical absorption measurement performed with light perpendicular to the (0 1 0) crystal face of a red block-shaped crystal of K₂CuSbS₃ indicates an experimental indirect band gap of 2.2 eV.     

Synthesis, structure, and ionic conductivity of Na5Li3Ti2S8

The compound Na₅Li₃Ti₂S₈ has been synthesized by the reaction of Ti with a Na/Li/S flux at 723 K. Na₅Li₃Ti₂S₈ crystallizes in a new structure type with four formula units in space group C2/c of the monoclinic system. The structure contains three crystallographically independent Na⁺ cations and two crystallographically independent Li⁺ cations. Na₅Li₃Ti₂S₈ possesses a channel structure that features two-dimensional layers built from Li(1)S₄ and TiS₄ tetrahedra. The layers, which are stacked along c, comprise eight-membered rings and sixteen-membered rings. Na(3)⁺ cations are located between the eight-membered rings and Na(1)⁺, Na(2)⁺, and Li(2)⁺ cations are located between the sixteen-membered rings. These cations are each octahedrally coordinated by six S²⁻ anions. The ionic conductivity σ_T of Na₅Li₃Ti₂S₈ ranges from 8.8×10⁻⁶ S/cm at 303 K to 3.8×10⁻⁴ S/cm at 483 K. The activation energy E_a is 0.40 eV.     

KBiMS4 (M=Si, Ge): Synthesis, structure, and electronic structure

Two new bismuth sulfides KBiSiS₄ and KBiGeS₄ have been synthesized by means of the reactive flux method. They adopt the RbBiSiS₄ structure type and crystallize in space group P2₁/c of the monoclinic system. The structure consists of (M=Si, Ge) layers separated by bicapped trigonal-prismatically coordinated K atoms. The M atom is tetrahedrally coordinated to four S atoms and the Bi atom is coordinated to a distorted monocapped trigonal prism of seven S atoms. The optical band gap of 2.25(2) eV for KBiSiS₄ was deduced from the diffuse reflectance spectrum. From a band structure calculation, the optical absorption for KBiSiS₄ originates from the layer. The Si 3p orbitals, Bi 6p orbitals, and S 3p orbitals are highly hybridized near the Fermi level. The orbitals of K have no contributions on both the upper of valence band and the bottom of conduction band.     

Synthesis, crystal structure and electrical characterization of two new potassium uranyl molybdates K2(UO2)2(MoO4)O2 and K8(UO2)8(MoO5)3O6

Two new potassium uranyl molybdates K₂(UO₂)₂(MoO₄)O₂ and K₈(UO₂)₈(MoO₅)₃O₆ have been obtained by solid state chemistry . The crystal structures were determined by single crystal X-ray diffraction data, collected with MoKα radiation and a charge coupled device (CCD) detector. Their structures were solved using direct methods and Fourier difference techniques and refined by a least square method on the basis of F² for all unique reflections, with R₁=0.046 for 136 parameters and 1412 reflections with I?2σ(I) for K₂(UO₂)₂(MoO₄)O₂ and R₁=0.055 for 257 parameters and 2585 reflections with I?2σ(I) for K₈(UO₂)₈(MoO₅)₃O₆. The first compound crystallizes in the monoclinic symmetry, space group P2₁/c with a=8.250(1) Å, b=15.337(2) Å, c=8.351(1) Å, β=104.75(1)°, ρ_mes=5.22(2) g/cm³, ρ_cal=5.27(2) g/cm³ and Z=4. The second material adopts a tetragonal unit cell with a=b=23.488(3) Å, c=6.7857(11) Å, ρ_mes=5.44(3) g/cm³, ρ_cal=5.49(2) g/cm³, Z=4 and space group P4/n.In both structures, the uranium atoms adopt a UO₇ pentagonal bipyramid environment, molybdenum atoms are in a MoO₄ tetrahedral environment for K₂(UO₂)₂(MoO₄)O₂ and MoO₅ square pyramid coordination in K₈(UO₂)₈(MoO₅)₃O₆. These compounds are characterized by layered structures. The association of uranyl ions (UO₇) and molybdate oxoanions MoO₄ or MoO₅, give infinite layers [(UO₂)₂(MoO₄)O₂]²⁻ and [(UO₂)₈(MoO₅)₃O₆]⁸⁻ in K₂(UO₂)₂(MoO₄)O₂ and K₈(UO₂)₈(MoO₅)₃O₆, respectively. Conductivity properties of alkali metal within the interlayer spaces have been measured and show an Arrhenius type evolution.     

Synthesis,crystal structure,and magnetic properties of the oxometallates KBaMnO4 and KBaAsO4

Single crystals of KBaMnO₄ and KBaAsO₄ were grown using the hydroflux method and characterized by single crystal X-ray diffraction. Both compounds crystallize in the orthorhombic space group Pnma with a = 7.7795(4) Å, b = 5.8263(3) Å, and c = 10.2851(5) Å for the manganate and a = 7.7773(10) Å, b = 5.8891(8) Å, and c = 10.3104(13) Å for the arsenate. The materials exhibit a three-dimensional crystal structure consisting of isolated MnO₄³⁻ or AsO₄³⁻ tetrahedra, with the charge balance maintained by K⁺ and Ba²⁺. Each tetrahedron is surrounded by six K⁺ and five Ba²⁺, and shares its corner/edge with KO₁₀ polyhedra and corner/edge/face with BaO₉ polyhedra, respectively. The crystal growth, crystal structure and magnetic properties are discussed.     

Mild hydrothermal synthesis, crystal structure, thermal behaviour, spectroscopic and magnetic properties of (NH4)0.80Li0.20[Fe(AsO4)F]

The (NH₄)_0.80Li_0.20[Fe(AsO₄)F] compound has been synthesized under mild hydrothermal conditions. The compound crystallize in the orthorhombic Pna2₁ space group, with cell parameters a=13.352(9), b=6.7049(9), c=10.943(2) Å and Z=8. The compound belongs to the KTiO(PO₄) structure type, with chains alternating FeO₄F₂ octahedra and AsO₄ tetrahedra, respectively, running along the “a” and “b” crystallographic axes. The diffuse reflectance spectrum in the visible region shows the forbidden electronic transitions characteristic of the Fe(III) d⁵-high spin cation in slightly distorted octahedral geometry. The Mössbauer spectrum at room temperature is characteristic of iron (III) cations. The ESR spectra, carried out from room temperature to 200 K, remain isotropic with variation in temperature; the g-value being 1.99(1). Magnetic measurements indicate the predominance of strong antiferromagnetic interactions.     

Bi2/3Ce1/3Rh2O5: A new mixed-valent Rh oxide with hitherto unknown structure

The new compound Bi_2/3Ce_1/3Rh₂O₅ has been discovered. It is currently the only known compound in the Bi-Ce-Rh-O system, and it crystallizes in a previously unknown structure type. The structure was established from single crystal X-ray diffraction data. Interatomic distances indicate the oxidation states as Bi_2/3³⁺Ce_1/3⁴⁺Rh₂^3.33+O₅. The structure indicates no ordering between Rh³⁺ and Rh⁴⁺. The lack of charge ordering is consistent with the metallic properties determined from electrical conductivity, Seebeck coefficient, and magnetic susceptibility measurements.     

Synthesis, crystal structure, and nonlinear optical properties of Bi2Cu5B4O14

Bi₂Cu₅B₄O₁₄ crystallizes in the noncentrosymmetric triclinic space group P1 (No. 1) with cell parameters a=10.1381(11) Å, b=9.3917(11) Å, c=3.4566(4) Å, α=105.570(2)°, β=92.275(2)°, γ=107.783(2)°, Z=1 and R₁=0.0401 and wR₂=0.0980. It is a layered structure that is built up from sheets of rectangular CuO₄ and trigonal BO₃ groups. The sheets are connected by infinite chains of edge shared BiO₆ polyhedra that intersect the bc plane at an angle slightly greater than 90°. The second-harmonic generation efficiency of Bi₂Cu₅B₄O₁₄, using 1064 nm radiation, is about one half times that of KH₂PO₄.     

An organosilyl derivative of trivacant tungstophosphate. Synthesis, characterization and crystal structure determination of α-A-[NBu4]3[PW9O34(C2H5SiO)3(C2H5Si)]

In the presence of NBu₄ⁿBr acting as phase-transfer reagent, organosilicon trichloride C₂H₅SiCl₃ reacts in acetonitrile with the trivacant tungstophosphate sodium salt β-A-Na₈H[PW₉O₃₄]·24H₂O to give hybrid organosilyl polyoxotungstate derivative α-A-[NBu₄ⁿ]₃[PW₉O₃₄(C₂H₅SiO)₃(C₂H₅Si)]. X-ray single crystal structural analysis indicates that the title compound is monoclinic, space group Cc, with lattice constants a=26.828(5), b=22.459(5), c=17.517(4) Å, β=103.19(3)°, V=10,276(4) Å³, Z=4, R=0.0462. According to the result of X-ray single crystal diffraction and chemical analysis, the hybrid polyanion consists of one α-A-[PW₉O₃₄]⁹⁻ framework on which are grafted simultaneously three RSiO groups through six Si-O-W bridge bonds, each of which is attached to the fourth RSi group through three Si-O-Si bridge bonds. The hybrid polyanion becomes a partial saturated, closed cage structure and also has an assembly of virtual C_3V symmetry.     

Synthesis, structure and physical properties of reduced barium titanate Ba2Ti13O22

Polycrystalline sample of the reduced barium titanate Ba₂Ti₁₃O₂₂ was synthesized by solid state reaction at 1523 K in Ar atmosphere for the first time. The Rietveld refinement using the powder X-ray diffraction data confirmed the sample to be main phase of Ba₂Ti₁₃O₂₂ having the orthorhombic crystal system, space group Bmab and the lattice parameters of a=11.67058(11) Å, b=14.12020(13) Å and c=10.06121(9) Å, and V=1657.995(20) ų. The valence state of Ti was evaluated by both the Ti–O bond distance analysis and the Ti K-edge XANES analysis. The magnetic susceptibility was nearly temperature independent in the range of 60–300 K, suggesting the Van Vleck Paramagnetism. The electrical conductivity at 300 K is approximately 320.50 S/cm, and a semiconducting behavior was observed below room temperature. The Seebeck coefficient showed a negative value of −1.25 μV/K at 300 K, indicating n-type behavior. These facts were confirmed by the results of the present theoretical calculations by the FLAPW method.     

Synthesis, structure, optical properties, and electronic structure of NaLiCdS2

The new compound NaLiCdS₂ has been synthesized by the reaction of Cd and a Li₂S/S/Na₂S flux at 773 K. This compound, which has the Ce₂O₂S structure type, crystallizes with one formula unit in space group P3¯m1 of the trigonal system in a cell at T=153 K with a=4.1320(3) Å and c=6.8666(11) Å. The structure consists of two-dimensional layers stacked perpendicular to the [001] direction. The two-dimensional layers are formed by corner-sharing LiS₄ or CdS₄ tetrahedra. The Na atoms are between these layers. Li incorporation in the compound is confirmed by an SIMS chemical composition map and by ICP measurements. The Li and Cd atoms are disordered in the crystal structure. First-principles calculations show that the optical excitations arise primarily from S→Cd charge-transfer transitions at 1.0 eV (very weak) and 2.4 eV (strong). Calculations also indicate that Na contributions around the Fermi level are significant. Polarized single-crystal optical measurements indicate an indirect optical band gap of 2.37 eV for light perpendicular to the (001) crystal face, in good agreement with theory. The compound NaLiZnS₂ has also been synthesized and is found to be isostructural with NaLiCdS₂.     

Synthesis, structure and magnetic properties of Na6Co2O6

Na₆Co₂O₆ was synthesized via the azide/nitrate route by reaction between NaN₃, NaNO₃ and Co₃O₄. Stoichiometric mixtures of the starting materials were heated in a special regime up to 500°C and annealed at this temperature for 50 h in silver crucibles. Single crystals have been grown by subsequent annealing of the reaction product at 500°C for 500 h in silver crucibles, which were sealed in glass ampoules under dried Ar. According to the X-ray analysis of the crystal structure (, Z=1, a=5.7345(3), b=5.8903(3), c=6.3503(3) Å, α=64.538(2), β=89.279(2), γ=85.233(2)°, 1006 independent reflections, R₁=8.34% (all data)), cobalt is tetrahedrally coordinated by oxygen. Each two CoO₄ tetrahedra are linked through a common edge forming Co₂O₆^6- anions. Cobalt ions within the dimers, being in a high spin state (S=2), are ferromagnetically coupled (J=17 cm^-1). An intercluster spin exchange (zJ′=−4.8 cm^-1) plays a significant role below 150 K and leads to an antiferromagnetically ordered state below 30 K. Heat capacity exhibits a λ-type anomaly at this temperature and yields a value of 19.5 J/mol K for the transition entropy, which is in good agreement with the theoretical value calculated for the ordering of the ferromagnetic-coupled dimers. In order to construct a model for the spin interactions in Na₆Co₂O₆, the magnetic properties of Na₅CoO₄ have been measured. This compound features isolated CoO₄ tetrahedra and shows a Curie-Weiss behavior (μ=5.14 μ_B, Θ=−20 K) down to 15 K. An antiferromagmetic ordering is observed in this compound below 10 K.