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.     

Synthesis, structure, and magnetic and electronic properties of Cs2Hg2USe5

The compound Cs₂Hg₂USe₅ was obtained from the solid-state reaction of U, HgSe, Cs₂Se₃, Se, and CsI at 1123 K. This material crystallizes in a new structure type in space group P2/n of the monoclinic system with a cell of dimensions a=10.276(6) Å, b=4.299(2) Å, c=15.432(9) Å, β=101.857(6) Å, and V=667.2(6) Å³. The structure contains layers separated by Cs atoms. Within the layers are distorted HgSe₄ tetrahedra and regular USe₆ octahedra. In the temperature range of 25-300 K Cs₂Hg₂USe₅ displays Curie-Weiss paramagnetism with μ_eff=3.71(2) μ_B. The compound exhibits semiconducting behavior in the [010] direction; the conductivity at 298 K is 3×10⁻³ S/cm. Formal oxidation states of Cs/Hg/U/Se may be assigned as +1/+2/+4/− 2, respectively.     

Darstellung,Kristallstruktur und Eigenschaften von Ln3AuO6 (Ln = Sm,Eu, Gd)

Syntheses, Crystal Structures, and Properties of Ln₃AuO₆ (Ln = Sm, Eu, Gd) The title compounds have been prepared from amorphous Au₂O₃ · x H₂O (x = 1–3) and Ln₂O₃ (Ln = Nd, Sm, Eu) via solid state reaction under elevated oxygen pressure adding KOH as mineralizing agent. They crystallize in a new structure type (triclinic, P1, Z = 1, Sm₃AuO₆: a = 3.7272(2) Å, b = 5.6311(2) Å, c = 7.0734(3) Å, α = 90.32(2)°, β = 103.983(3)°, γ = 90.822(2)°, 125 powder intensities, R_p = 2.57%, Eu₃AuO₆: a = 3.7012(2) Å, b = 5.6134(2) Å, c = 7.0652(4) Å, α = 90.838(3)°, β = 102.956(3)°, γ = 90.909(2)°, 122 powder intensities, R_p = 3.16%, Gd₃AuO₆: a = 3.6720(2) Å, b = 5.5977(2) Å, c = 7.0636(2) Å, α = 90.509(2)°, β = 102.889(3)°, γ = 91.068(2)°, 3424 reflections, R₁ = 12.90%). The crystal structure was solved and refined from single crystal data of Gd₃AuO₆. The structures of Sm₃AuO₆ and Eu₃AuO₆ were refined from powder diffraction data. The isolated square planar AuO₄ units are stacked along the a‐axis and are linked by LnO₆‐ and LnO₆₊₁‐polyhedra. One of the oxygen atoms is exclusively coordinated by trivalent lanthanides, in tetrahedral geometry. The lanthanoid aurates decompose between 700 and 900 °C into Ln₂O₃, Au and O₂. The magnetic moments μ_eff(Gd₃AuO₆) = 7.9 μ_B and, at 20 °C respectively, μ_eff(Sm₃AuO₆) = 1.55 μ_B as well as μ_eff(Eu₃AuO₆) = 3.5 μ_B confirm that the lanthanides are trivalent. The UV/VIS absorption spectra can be interpreted at assuming free ions.     

Preparation and Crystal Structures of Ternary Rare Earth Osmium Gallides LnOsGa3 (Ln = Gd—Tm) and LnOsGa3 (Ln = La—Nd)

The title compounds were prepared from the elemental components at high temperatures. The compounds LnOsGa₃ crystallize with the cubic TmRuGa₃ type structure which was refined from four‐circle X‐ray diffractometer data of TbOsGa₃: Pm3¯m, Z = 3, a = 640.8(1) pm, R = 0.014 for 173 structure factors and 10 variable parameters. The other gallides crystallize with a new structure type which was determined from single‐crystal X‐ray data of CeOsGa₄: Pmma, Z = 6, a = 963.9(2) pm, b = 880.1(1) pm, c = 767.0(1) pm, R = 0.030 for 744 F values and 56 variables. The structure may be considered as consisting of two kinds of alternating layers, although bonding within and between the layers is of similar strength. One kind of layers (A) is slightly puckered, two‐dimensionally infinite, hexagonal close packed, with the composition OsGa₃; the other kind of layers (B) is planar with the composition CeGa. The structure is closely related to that of Y₂Co₃Ga₉ where the corresponding layers have the compositions Co₃Ga₆ (A) and Y₂Ga₃ (B).     

A theoretical study of electronic and vibrational properties of neutral,cationic, and anionic B24 clusters

The equilibrium geometries, electronic and vibrational properties, and static polarizability of B₂₄, B, and B clusters are reported here. First‐principles calculations based on density functional theory predict the staggered double‐ring configuration to be the ground state for B₂₄, B, and B, in contrast to the quasi‐planar structure observed in small neutral and ionized B_n clusters with n ≤ 15. Furthermore, the (4 × B₆) tubular structure is found to be relatively stable in comparison to the 3D cage structure. The presence of delocalized π and multicentered σ bonds appears to be the cause of the stability of the double‐ring and tubular isomers. For the ground state of B₂₄, the lower and upper bound of the electron affinity is 2.67 and 2.81 eV, respectively, and the vertical ionization potential is 6.88 eV. Analysis of the frequency spectrum of the double‐ring and tubular isomers reveals the characteristic vibrational modes typically observed in carbon nanotubes. The corresponding IR spectrum also reflects the presence of some of these characteristic modes in the neutral and ionized B₂₄, suggesting that double‐ring and tubular structures can be considered as the building blocks of boron nanotubes. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Synthesis,Crystal Structure,and Physical Properties of the New Chain Alkalioxocuprate K3Cu2O4

Single crystals of K₃Cu₂O₄ were prepared by the azide/nitrate route from respective stoichiometric mixtures of KN₃, KNO₃ and CuO, at 923 K, whereas powder samples were synthesised by solid state reaction of K₂O, KCuO₂ and CuO, sealed in gold ampoules and treated at 723 K. According to the single crystal structure analysis (Cmcm, Z = 4, a = 6.1234(1), b = 8.9826(2), c = 10.8620(2) Å, R₁ = 0.044, R₂ = 0.107), the main structural feature are undulating CuO₂ chains built up from planar, edge sharing CuO₄ square units. From an analysis of the Cu–O bond lengths, the valence state of either +2 or +3 can be unambiguously assigned to each copper atom. The magnetic susceptibilities show the dominance of antiferromagnetic (AFM) interactions. At high temperatures, the magnetic behaviour can be fitted with the Curie–Weiss law (μ_eff = 1.84μ_B, Θ = –105 K). The experimental data can be very well described by a uniform Heisenberg chain with a nearest‐neighbour spin intrachain interaction (J_nn) of ~ 101 K.     

CeAgAs2 — a New Derivative of the HfCuSi2 Type of Structure: Synthesis,Crystal Structure and Magnetic Properties

Single crystals of CeAgAs₂ have been obtained by chemical transport reactions starting from a pre‐reacted powder sample. The crystal structure was solved using X‐ray diffraction (space group Pmca, No. 57, a = 5.7586(4) Å, b = 5.7852(4) Å, c = 21.066(3) Å, Z = 8) and refined to a residual of R(F) = 0.029 for 46 refined parameters and 1020 reflections. The structure of CeAgAs₂ represents a new distorted and ordered variant of the HfCuSi₂ type. The characteristic feature of this structure are infinite cis‐trans chains of As atoms with As—As distances of 2.563(1) Å and 2.601(1) Å. CeAgAs₂ is paramagnetic (μ_eff = 2.37 μ_B, θ = —10.5(2) K), with antiferromagnetic ordering at 5.5(2) K and exhibits a metamagnetic transition starting at 4.6 kOe and T = 1.8 K.     

Preparation,Crystal Structure,Physical Properties and Electronic Band Structure of TlScQ2 (Q = S,Se and Te)

The title compounds were prepared by reaction of Tl₂Q (Q = S, Se and Te) Sc and Q in the temperature range of 200 to 500 °C. The structures of the selenide and the telluride adopt the α‐NaFeO₂ type, while TlScS₂ crystallizes in the β‐RbScO₂ type structure. The space group is for TlScSe₂ and TlScTe₂ with a = 3.9370(4) Å, c = 23.194(5) Å, and a = 4.2129(4) Å, c = 24.099(3) Å, respectively. The sulphide crystallizes in P6₃/mmc with a = 3.761(3) Å and c = 14.942(4) Å. The crystal chemical relations between the three chalcogenides are discussed. According to the electrical measurements and the band structure calculations, the compounds are semiconductors or poor metals.     

Structure and physical properties of nonstoichiometric rare-earth cadmium antimonides, RECd1−xSb2 (RE=La, Ce, Pr, Nd, Sm)

The ternary rare-earth cadmium antimonides RECd_1−xSb₂ (RE=La, Ce, Pr, Nd, Sm) were prepared by reaction of the elements at 1000 °C. The presence of Cd defects, previously found for LaCd_0.700(5)Sb₂ and CeCd_0.660(4)Sb₂, has been confirmed by single-crystal X-ray diffraction studies for the isotypic compounds PrCd_0.665(3)Sb₂, ), NdCd_0.659(3)Sb₂, ), and SmCd_0.648(3)Sb₂, ). These compounds adopt the HfCuSi₂-type structure (Pearson symbol tP8, space group P4/nmm, Z=2). The electrical and magnetic properties of samples with nominal composition RECd_0.7Sb₂ were investigated. All exhibit metallic behaviour, but CeCd_0.7Sb₂ undergoes an abrupt drop in its electrical resistivity below 3 K. LaCd_0.7Sb₂ exhibits temperature-independent Pauli paramagnetism and SmCd_0.7Sb₂ displays van Vleck paramagnetism. The remaining compounds obey the modified Curie-Weiss law at high temperatures. CeCd_0.7Sb₂ undergoes ferromagnetic ordering below 3 K, reaching a saturation magnetization of ∼1.0 μ_B, whereas PrCd_0.7Sb₂ and NdCd_0.7Sb₂ remain paramagnetic down to 2 K.     

Syntheses and structures of six compounds in the A2LiMS4 (A=K, Rb, Cs; M=V, Nb, Ta) family

Six new compounds in the A₂LiMS₄ (A=K, Rb, Cs; M=V, Nb, Ta) family, namely K₂LiVS₄, Rb₂LiVS₄, Cs₂LiVS₄, Rb₂LiNbS₄, Cs₂LiNbS₄, and Rb₂LiTaS₄, have been synthesized by the reactions of the elements in Li₂S/S/A₂S₃ (A=K, Rb, Cs) fluxes at 773 K. The A and M atoms play a role in the coordination environment of the Li atoms, leading to different crystal structures. Coordination numbers of Li atoms are five in K₂LiVS₄, four in A₂LiVS₄ (A=Rb, Cs) and Cs₂LiNbS₄, and both four and five in Rb₂LiMS₄ (M=Nb, Ta). The A₂LiVS₄ (A=Rb, Cs) structure comprises one-dimensional chains of tetrahedra. The Rb₂LiMS₄ (M=Nb, Ta) structure is composed of two-dimensional layers. The Cs₂LiNbS₄ structure contains one-dimensional chains that are related to the Rb₂LiMS₄ layers. The K₂LiVS₄ structure contains a different kind of layer.     

Die Kristallstrukturen von KNdTe4, RbPrTe4 und RbNdTe4 — Untersuchungen zur thermischen Stabilität von KNdTe4 sowie Bemerkungen zu einigen anderen Vertretern der Zusammensetzung ALnTe4 (A = K,Rb, Cs und Ln = Seltenerd‐Metall)

Crystal Structures of KNdTe₄, RbPrTe₄, and RbNdTe₄ — Investigations concerning the Thermal Stability of KNdTe₄ as well as some Remarks concerning Additional Representatives of the Composition ALnTe₄ (A = K, Rb, Cs and Ln = Rare Earth Metal) Of the compounds ALnQ₄ (A = Na, K, Rb, Cs; Ln = Lanthanoid; Q = S, Se and Te) the crystal structures of the three new tellurides KNdTe₄, RbPrTe₄ and RbNdTe₄ were determined by X‐ray single‐crystal structure analysis and of the three additional new ones KCeTe₄, KPrTe₄ and CsNdTe₄ by X‐ray powder diffraction experiments. All six new compounds are isotypic with KCeSe₄. Characteristic for the crystal structure of the compounds mentioned above are layers built from (Q₂)^2— dumbbells in form of 4.3².4.3 nets with embedded cations A⁺ and Ln³⁺ between them, which are coordinated eightfold in form of square‐shaped antiprisms by Q ions. The distances Te‐Te within the dumbbells were found to be 277.8(2) pm for all investigated tellurides. By combination of X‐ray diffraction and DTA measurements it was shown that the compound KNdTe₄ is metastable at ambient temperature with a limited existence range between the temperatures 260 and 498 °C.     

Synthesis,Crystal Structure and Properties of Li2Cu5(PO4)4

Li₂Cu^II₅(PO₄)₄ has been obtained by various reactions starting from copper or Cu₂O. Crystallization was achieved using I₂ as oxidant and mineralizer. The new orthophosphate crystallizes in space group P$\bar{1}$ , Z = 2, with a = 6.0502(3) Å, b = 9.2359(4) Å, c = 11.4317(5) Å, α = 75.584(2)°, β = 80.260(2)°, γ = 74.178(2)°, at 293 K. Its structure has been determined from X‐ray single‐crystal data and refined to R₁ = 0.022{wR₂ = 0.058 for 4633 unique reflections with F_o > 4σ (F_o)}. From magnetic measurements μ_eff = 1.51 μ_B/Cu and θ_P = –37.4 K have been determined. The Vis/NIR spectrum of aqua‐green Li₂Cu₅(PO₄)₄ shows a single broad band centered around $\bar{1}$ = 12000 cm^–1. Magnetic behavior and spectrum are discussed within the angular overlap model.     

Synthesis,Crystal Structure and Properties of Na2MnO2

Na₂MnO₂ was prepared via the azide/nitrate route. Stoichiometric mixtures of the precursors (Mn₂O₃, NaN₃ and NaNO₃) were heated in an appropriate regime up to 390 °C and annealed at this temperature for 20 h, in specially designed silver containers. As the most prominent feature, the crystal structure of Na₂MnO₂ (C2/c, Z = 12, a = 12.5026(9), b = 12.1006(9), c = 6.0939(4) Å, β = 117.94(0)°, 1556 independent reflections, R₁ = 3.83 % (all data)) forms a three dimensional framework polyanion of corner sharing MnO₄‐tetrahedra. The connectivity pattern of the tetrahedral building units corresponds to the moganite structure, a rare SiO₂ modification. According to measurements of the magnetic susceptibility in the temperature range from 2 to 750 K, Na₂MnO₂ shows antiferromagnetic ordering below 250 K. Evaluation of the high temperature data employing the Curie‐Weiss law revealed a magnetic moment of μ_eff = 5.93 μ_B, confirming the presence of divalent manganese.     

Refined Crystal Structures of SrLnCuS<Subscript>3</Subscript> (Ln = Er,Yb)

According to powder X-ray diffraction data, the crystal structures of compounds SrLnCuS₃ (Ln = Er, Yb) have been refined by minimizing the derivative difference in the anisotropic approximation for all atoms. Crystals are orthorhombic, space group Cmcm, structure type KZrCuS₃: a = 3.93128(3) Å, b = 12.9709(1) Å, c = 10.1161(1) Å, V = 515.843(9) ų, ρ_calc = 5.337 g/cm³, Z = 4, R_DDM = 3.73%, R_F = 2.06% (SrErCuS₃); a = 3.91448(4) Å, b = 12.9554(1) Å, c = 10.0332(1) Å, V = 508.842(8) Å3, ρ_calc = 5.487 g/cm³, Z = 4, R_DDM = 3.56%, R_F = 1.48% (SrYbCuS₃). The structure of SrLnCuS₃ is described by [LnCuS₃] twodimensional layers formed by distorted CuS₄ tetrahedra and LnS₆ octahedra with Sr²⁺ ions residing between the layers. The compounds are transparent for IR radiation in the range 3200–1800 cm^–1.     

Tt‐Tt (Tt = Si,Ge) Dumb‐Bell Structures at Different Valence Electron Concentrations: Ln2MgSi2 (Ln = La,Ce), Yb2Li0.5Ge2, and Yb1.75Mg0.75Si2

The isostructural compounds Yb₂MgSi₂, La_2.05Mg_0.95Si₂, and Ce_2.05Mg_0.95Si₂, as well as Yb₂Li_0.5Ge₂ and Yb_1.75Mg_0.75Si₂, respectively, were synthesized from stoichiometric mixtures of the corresponding elements in sealed Nb‐ ampoules under argon atmosphere. The structures were determined by single crystal X‐ray diffraction: Yb₂MgSi₂ (P4/mbm (No. 127), a = 7.056(1), c = 4.130(1) ų, Z = 2), La_2.05Mg_0.95Si₂ (P4/mbm, a = 7.544(1), c = 4.464(1) ų, Z = 2), and Ce_2.05Mg_0.95Si₂ (P4/mbm, a = 7.425(1), c = 4.370(1) ų, Z = 2), Yb₂Li_0.5Ge₂ (Pnma (No. 62), a = 7.0601(6), b = 14.628(1), c = 7.6160(7) Å, V = 786.5ų, Z = 4), Yb_1.75Mg_0.75Si₂ (Pnma, a = 6.9796(1), b = 14.4009(1), c = 7.5357(1) Å, V = 757.43(2) ų, Z = 4). All compounds contain exclusively Tt‐Tt dumb‐bells (Tt = Si, Ge). The Si‐Si Zintl anions exhibit only very small variations of bond lengths which seem to be more due to cation matrix effects than to effective bond orders.     

Synthesis,Crystal Structure and Magnetism of the New Oxysulfide Ce3NbO4S3

The orange cerium‐niobium‐oxysulfide Ce₃NbO₄S₃ was synthesized by the solid state reaction of CeO₂, Ce‐metal, Nb₂O₅ and sulfur at 1100 °C. The crystal structure has orthorhombic symmetry (space group Pbam, a = 7.055(1), b = 14.571(3), c = 7.627(2) Å, Z = 4) and contains isolated [Nb₂S₄O₆]¹⁰⁻ ions consisting of two strongly distorted, edge sharing NbO₃SS_2/2 octahedra. Niobium is connected to three oxygen and three sulfur atoms. The cerium atoms are eightfold coordinated by oxygen and sulfur atoms. Certain oxygen and sulfur atoms are not connected to niobium, but exclusively surrounded by cerium. By connecting these cation polyhedra, one recognizes layers of polycations perpendicular to the c‐axis. The magnetic susceptibility shows Curie‐Weiss behavior with an effective magnetic moment μ_eff = 2.63(1) μ_B/Ce in agreement with Ce³⁺. A Weiss‐constant θ_p = –12(1) K indicates weak antiferromagnetic coupling. No magnetic ordering was detected above 2 K.     

Alkalimetallbismutide ABi und ABi2 (A = K,Rb, Cs) — Synthesen,Kristallstrukturen, Eigenschaften

Alkali Metal Bismuthides ABi and ABi₂ — Synthesis, Crystal Structure, Properties The Zintl phases ABi (A = K/Rb/Cs; monoclinic, space group, P2₁/c, a = 1422.3(2)/1474.2(2)/1523.7(3), b = 724.8(1)/750.2(1)/773.7(1), c = 1342.0(2)/1392.1(2)/1439.9(2) pm and β = 113.030(3)/113.033(2)/112.722(3)°, Z = 16) crystallize with the β‐CsSb structure type containing chains of two‐connected Bi atoms. Hence, and according to calculated electronic structures, they are semiconductors with small band gaps of approx. 0.5 eV. In contrast, the compounds ABi₂ (A = K/Rb/Cs; cubic, space group Fd3¯m, a = 952.1(2)/962.4(8)/972.0(3) pm, Z = 8) belong to the Laves phases, showing a typical metallic electrical conductivity and no band gaps.     

Synthesis,Crystal Structure and Properties of RbMnO2

RbMnO₂ was prepared via the azide/nitrate route. Stoichiometric mixtures of the precursers (Mn₂O₃, RbN₃ and RbNO₃) were heated in a special regime up to 600 °C and annealed at this temperature for 30 h in specially designed silver crucibles. Single crystals have been grown by annealing a 1:1 mixture of Rb₂O and MnO_x at 585 °C for 1200 h. According to the crystal structure determination Mn³⁺ is in a square‐pyramidal coordination by oxygen. These [MnO₅] units form double chains extending along the crystallographic c‐axis. RbMnO₂ shows Curie‐Weiss behaviour down to ～ 100 K. A fit of the susceptibility data yields an average value of the magnetic moment (per manganese atom) of μ_eff = 5.33 μ_B, and θ_p = –820 K. At 50 K and low field strength onset of ferromagnetic order due to spin canting has been observed.     

Hydrothermal Synthesis of Rare Earth Iodates from the Corresponding Periodates: II1). Synthesis and Structures of Ln(IO3)3 (Ln = Pr,Nd, Sm,Eu, Gd,Tb, Ho,Er) and Ln(IO3)3 · 2H2O (Ln = Eu,Gd, Dy,Er, Tm,Yb)

Single crystals of lanthanide iodates have been quickly grown by decomposition of the corresponding periodates under hydrothermal conditions. Single crystal X‐ray diffraction showed that two structure types form with the elements from Pr‐Yb, an anhydrous form for Pr, Nd, Sm, Eu, Gd, Tb, Ho, Er and a dihydrate for Eu, Gd, Dy, Er, Tm, Yb. A detailed structure study is presented for one representative of each of these types, along with structure type and lattice parameters for the other materials. Tb(IO₃)₃: Space group P2₁/c, Z = 4, lattice dimensions at 120 K: a = 7.102(1), b = 8.468(1), c = 13.355(2)Å, β = 99.67(1)°; R1 = 0.034. Yb(IO₃)₃ · 2H₂O: Space group P1¯, Z = 2, lattice dimensions at 120 K: a = 7.013(1), b = 7.370(1), c = 10.458(2)Å, α = 95.250(5), β = 105.096(5), γ = 109.910(10)°; R1 = 0.024.     

Synthesis and Crystal Structure of Commensurate Polymorph of Ln4AlCu2B9O23 (Ln=Lu,Ho) and Refinement of Cu2Al6B4O17

Single crystals of new Cu,Lu(Ho)–alumoborate and known Cu,Al–borate were synthesized through reaction between CuB₂O₄ and LnBO₃ on the Al₂O₃ surface by annealing at 1100 °C. Structure of commensurate modification of Ln₄AlCu₂B₉O₂₃, (Ln = Lu,Ho), sp. gr. , was solved at room temperature. It was found that a low–temperature (110 K) modification possesses incommensurate modulations with modulation vector q =(0, 0, 0.132). The nonaborate block – [B₉O₂₃]^19– – 9[6T+3Δ] forms an isolated unique dense closed anionic unit. This block is terminated by Al–tetrahedrons in the chessboard pattern, resulting in formation of complex alumoborate layer [AlB₉O₂₃]^16–. Apical oxygen of central BO₃ triangle of the nonaborate block seems to be the source of modulations observed in low temperature polymorph. Cationic layers with the Ln and Cu atoms are alternating along c axis with anionic layers. The structure Cu₂Al₆B₄O₁₇, previously studied by the Rietveld method, was corroborated by single crystal data and was compared with LiAl₇B₄O₁₇.