- Spectrum analysis of U3+-doped LaBr3 single crystals. Part 1: Crystal-field analysis
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Single crystals of U3+:LaBr3 were grown by the Bridgman-Stockbarger technique. High-resolution polarized absorption spectra of the crystals were recorded at 4.2 K in the 4000-50,000 cm-1 range. Sixty-four experimental crystal-field energy levels of the U3+ ion were fitted to a semiempirical Hamiltonian employing free-ion, one-electron crystal-field as well as two-particle correlation crystal-field (CCF) operators with an r.m.s. deviation of 28 cm-1. The performed analysis of the spectra enabled the determination of crystal-field parameters and assignment of the observed 5f3→5f3 transitions. The effects of selected CCF operators on the splitting of some specific U3+ multiplets have been investigated and the obtained values of Hamiltonian parameters are discussed and compared with those reported in previous analyses.
- Sobczyk, Marcin,Drozdzynski, Janusz,Karbowiak, Miroslaw
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- Room temperature fluorescence and excited state dynamics in the near infrared and visible region of U3+ doped LaBr3 single crystals
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Good quality U3+ doped LaBr3 single crystals with a 0.1 mol% U3+ nominal concentration have been obtained by the Bridgman-Stockbarger method. Luminescence spectra of the crystals were recorded in a wide spectral range at room temperature. Excitation in the 5f 26d1 spectral region produced a strong red and near infrared emission.
- Sobczyk, Marcin,Drozdzyński, Janusz,Lisiecki, Rados?aw,Solarz, Piotr,Ryba-Romanowski, Witold
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- La6Br10Fe: A La6Fe octahedron with a mixed M6X12/M6X8 type environment
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The title compound was synthesized from La, LaBr3, and Fe under Ar atmosphere at 800°C. It crystallizes in space group P41 (No. 76) with lattice constants a = 8.255(1) A and c = 30.033(6) A. The structure features an isolated Fe-centered La6 octahedron with all corners, 9 of its 12 edges, and 3 of its 8 triangular faces coordinated, bridged, or capped by Br atoms. The La6Fe octahedron is significantly distorted, and the La coordination by Br atoms deviates from the common close-packing arrangements found in other reduced rare earth metal halides. Band structure, bonding, and physical properties of the compound have been investigated.
- Zheng, Chong,Mattausch, Hansjuergen,Hoch, Constantin,Simon, Arndt
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- La8Br7Ni4: Ribbons of Ni hexagons in condensed La6 trigonal prisms
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A ternary lanthanum bromide La8Br7Ni4 was synthesized from La, LaBr3, and Ni under an Ar atmosphere at 830 °C. It crystallizes in space group C2/m (No. 12) with lattice constants a = 29.528(4) A, b = 4.0249(6), c = 8.708(1) A, and β = 94.515(2)°. The structure features condensed Ni-centered La6 trigonal prisms. The Ni atoms are bonded to each other to form ribbons of Ni hexagons. Band structure, bonding, and physical properties of the compound have been investigated.
- Zheng, Chong,Mattausch, Hansjuergen,Hoch, Constantin,Simon, Arndt
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- Isolated and edge-sharing interstitially stabilized metal tetrahedra {M4Z} in La4ZBr7, M9Z 4I16, and BaM4Z2I8 (M = La,Ce). The nature of Z
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Metallothermic reductions of LaBr3, LaI3 and CeI 3 with barium metal resulted in single crystals of La 4ZBr7, M9Z4I16 and BaM4Z2I8 (M = La,Ce) as by-products, subject to apparently ubiquitous oxygen and/or nitrogen (= Z) impurities. The crystal structure of La4ZBr7 (1, orthorhombic, Pnma, Z = 4, a = 1212.4(1), b = 1404.8(2), c = 804.7(1) pm, R 1 = 0.0358 for I>2σI with N:O = 0.91:0.09) is determined by isolated {La4Z} tetrahedra surrounded by and connected through bromide ligands. In the crystal structure of Ce9Z4I 16 (2, orthorhombic, Fddd, Z = 8, a = 890.0(1), b = 2264.1(2), c = 4279.5(4) pm, R1 = 0.0262 for I>2σI with N:O = 0.75:0.25), {Ce4Z} tetrahedra are connected to {Ce4/2Z} chains via common edges and further to layers by iodide ligands. The layers are stacked and connected via the ninth cerium atom according to Ce[{Ce4/2Z}I 4]4. Similar {La4/2Z} chains and BaI 8/4 chains run perpendicularly to each other and are connected via common iodide ions in the crystal structure of BaLa4Z 2I8 = Ba2[{La4/2Z}I 4]4 (3, monoclinic, C2/c, Z = 4, a = 897.5(1), b = 2162.4(3), c = 1229.3(2), β = 110.32(1)°, R1 = 0.0261 for I>2σI with N:O = 0.54:0.46). The nature of the interstitial Z, oxygen and/or nitrogen, is evaluated.
- Gerlitzki, Niels,Hammerich, Stefanie,Pantenburg, Ingo,Meyer, Gerd
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- La3Br3Ni: Jahn-Teller distortion in the reduced rare earth metal halide
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A ternary lanthanum bromide La3Br3Ni was synthesized from lanthanum, LaBr3 and nickel under argon at 800 °C. It crystallizes in the tetragonal space group I4122 (No. 98) with lattice constants a = 12.1758(9) A a
- Zheng, Chong,Mattausch, Hansjuergen,Hoch, Constantin,Simon, Arndt
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- La9Sb16Br3 and Ce9Sb 16Cl3: Stars and stripes in rare earth halide and intermetallic compounds
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The title compounds were synthesized from Ln, LnX3 (Ln = La, Ce; X = Cl, Br), and Sb under an Ar atmosphere at 950°C. They crystallize in the space group P63/m (No. 176) with lattice constants a = 21.232(5) and 20.862(2) A and c = 4.323(2) and 4.2728(7) A for La9Sb 16Br3 and Ce9Sb16Cl3, respectively. The solids are the most metal-rich members in the reduced rare earth metal halide family and contain partial structures which are characteristic of reduced halides and intermetallic phases. These are the [Ln6X6]∞, hexagon stars, Sb-centered [Ln3Sb]∞ trigonal prismatic columns, and stripes of Sb square meshes. Computational analysis indicates that their electronic structure is valence-precise in the reduced halide part, but electron-deficient in the intermetallic part. Susceptibility and resistivity measurements reveal the metallic nature of the compounds.
- Zheng, Chong,Mattausch, Hansjuergen,Simon, Arndt
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- Molar volume and ionic conduction in molten LaBr3
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Prior to the measurements of physicochemical properties, bromination of La2O3 with NH4Br was attempted to obtain LaBr3 and study the optimum condition of this reaction. The molar volumes of the molten LaBr3 were measured in the range 1084 to 1122 K by dilatometry and fitted as a linear function by a least-squares method. The volume change on melting LaBr3 was evaluated from this result and the available crystallographic data to be 13.6%. The conductivities of molten LaBr3 were also measured by an a.c. technique and fitted by a quadratic function of temperature in the range 1088 to 1113 K. The molar conductivities were evaluated using the data of the molar volumes and conductivities. The results suggest that there exist some complexes in molten LaBr3 as well as LaCl3-6 in molten LaCl3.
- Fukushima, Kazuko,Iwadate, Yasuhiko
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- La4N2S3: A new nitride sulfide of lanthanum with unprecedented crystal structure
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The oxidation of lanthanum powder with sulfur and cesium azide (CsN 3) in the presence of lanthanum tribromide (LaBr3) yields lanthanum nitride sulfide with the composition La4N2S 3 when appropriate molar ratios of the reactants are used. Additional cesium bromide (CsBr) as a flux secures fast reactions (7 d) at 900 °C in evacuated silica tubes as well as the formation of almost black single crystals. The orthorhombic crystal structure (Pnnm, Z = 2) was determined from single crystal X-ray diffraction data (a = 641.98(4), b = 1581.42(9), c = 409.87(3) pm). Two crystallographically different La3+ cations are present, La1 resides in sixfold coordination of two N3- and four S2- anions forming a trigonal prism and La2 is coordinated by two N3- and five S2- in the shape of a monocapped trigonal prism. However, the main feature of the crystal structure comprises N3--centred (La 3+)4 tetrahedra which arrange as pairs [N 2La6]12+ of edge-shared [NLa4] 9+ units and which are further connected via four vertices to form double chains ∞1{[N2La 2La′4/2]6+}. They get bundled along [001] like a hexagonal rod packing and are held together by two crystallographically different S2- anions. Further motifs for the connectivity of [NM 4]9+ tetrahedra in crystal structures of nitride chalcogenides and halides of the rare-earth elements (M = Sc, Y, La; Ce - Lu) with ratios of N : M = 1 : 2 are presented and discussed for comparison.
- Lissner, Falk,Schleid, Thomas
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- Structural characterization of methanol substituted lanthanum halides
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The first study into the alcohol solvation of lanthanum halide [LaX3] derivatives as a means to lower the processing temperature for the production of the LaBr3 scintillators was undertaken using methanol (MeOH). Initially the de-hydration of {[La(μ-Br)(H2O)7](Br)2}2 (1) was investigated through the simple room temperature dissolution of 1 in MeOH. The mixed solvate monomeric [La(H2O)7(MeOH)2](Br)3 (2) compound was isolated where the La metal center retains its original 9-coordination through the binding of two additional MeOH solvents but necessitates the transfer of the innersphere Br to the outersphere. In an attempt to in situ dry the reaction mixture of 1 in MeOH over CaH2, crystals of [Ca(MeOH)6](Br)2 (3) were isolated. Compound 1 dissolved in MeOH at reflux temperatures led to the isolation of an unusual arrangement identified as the salt derivative {[LaBr2.75·5.25(MeOH)]+0.25 [LaBr3.25·4.75(MeOH)]-0.25} (4). The fully substituted species was ultimately isolated through the dissolution of dried LaBr3 in MeOH forming the 8-coordinated [LaBr3(MeOH)5] (5) complex. It was determined that the concentration of the crystallization solution directed the structure isolated (4 concentrated; 5 dilute) The other LaX3 derivatives were isolated as [(MeOH)4(Cl)2La(μ-Cl)]2 (6) and [La(MeOH)9](I)3·MeOH (7). Beryllium Dome XRD analysis indicated that the bulk material for 5 appear to have multiple solvated species, 6 is consistent with the single crystal, and 7 was too broad to elucidate structural aspects. Multinuclear NMR (139La) indicated that these compounds do not retain their structure in MeOD. TGA/DTA data revealed that the de-solvation temperatures of the MeOH derivatives 4-6 were slightly higher in comparison to their hydrated counterparts.
- Boyle, Timothy J.,Ottley, Leigh Anna M.,Alam, Todd M.,Rodriguez, Mark A.,Yang, Pin,Mcintyre, Sarah K.
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p. 1784 - 1795
(2010/07/03)
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- Rare earth ethenide-halides Ln2n+6(C2) n+4X2n+2: Preparation, crystal structure, intergrowth and twinning
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Preparation, crystal structure, intergrowth and twinning of the compounds La10(C2)6Br6, Ce10(C 2)Br6 and Gd10(C2) 6(Cl6 are described.
- Mattausch, Hansjuergen,Kienle, Lorenz,Duppel, Viola,Hoch, Constantin,Simon, Arndt
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p. 1527 - 1535
(2011/01/09)
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- A mass spectrometric study of the molecular and ionic sublimation of lanthanum tribromide
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The molecular and ionic composition of vapor over lanthanum tribromide was studied by high-temperature mass spectrometry under the conditions of sublimation from a Knudsen effusion cell and from an open single crystal surface. The partial pressures of LaBr3 and La2Br 6 in saturated vapor and the ratio between their sublimation coefficients under free vaporization conditions were determined. The second and third laws of thermodynamics were used to calculate the enthalpies of sublimation of LaBr3 in the form of monomers and dimers. In ionic sublimation studies, the emission of the Br-, LaBr 4 - , and La2Br 7 - negative ions was recorded in both regimes. Studies of the ionic sublimation of LnX3 single crystals were shown to give reliable data on the thermochemical properties of negative ions.
- Butman,Motalov,Kudin,Grishin,Kryuchkov,Kraemer
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p. 164 - 171
(2008/04/06)
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- Systematics and anomalies in rare earth/aluminum bromide vapor complexes: Thermodynamic properties of the vapor complexes LnAl3Br12 from Ln = Sc to Ln = Lu
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Systematics and anomalies in the rare earth/aluminum bromide vapor complexes have been investigated by the phase equilibrium-quenching experiments. The measurements suggest that the LnAl3Br12 complexes are the predominant vapor compl
- Wang, Zhi-Chang,Yu, Jin
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p. 4248 - 4255
(2008/10/09)
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- M3NS3 (M = La - Nd, Sm, Gd - Dy): Structure and magnetism of 3:1:3-type nitride sulfides of trivalent lanthanides
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Nitride sulfides of the trivalent lanthanides with the composition M 3NS3 (M = La - Nd, Sm, Gd - Dy) can be prepared by the oxidation of the respective lanthanide metal with sulfur, sodium azide (NaN 3), and the corresponding lanthanide tribromide (MBr3) when an additional flux (NaBr) is used. Temperature ranges from 800 to 900 °C for the thermal treatment of the reaction mixtures in evacuated silica tubes secure the formation of bright to dark brown, transparent, lath shaped single-crystals. The orthorhombic crystal structure (Pnma, Z = 4) was determined from single-crystal X-ray diffraction data (La3NS3: a = 1215.13(5), b = 415.90(2), c = 1322.12(5) pm, Ce3NS3: a = 1206.28(4), b = 410.16(1), c = 1307.18(5) pm, Pr3NS3: a = 1205.45(7), b = 405.35(2), c = 1297.58(8) pm, Nd3NS3: a = 1207.82(5), b = 401.31(1), c = 1295.20(4) pm, Sm3NS3: a = 1201.58(6), b = 394.84(2), c = 1285.63(7) pm, Gd3NS3: a = 1197.17(7), b = 388.22(3), c = 1286.92(8) pm, Tb3NS3: a = 1191.62(7), b = 385.07(3), c = 1282.44(8) pm, and Dy3NS3: a = 1187.66(7), b = 382.55(3), c = 1276.77(8) pm). There are three crystallographically different M3+ cations present in coordination of both the N3- and the S2- anions. However, [NM 4]9+ tetrahedra connected via two common corners (c) to form linear chains ∞1{[N(M1)1/1 t(M2)1/1t(M3)2/2c] 6+} along [010] build up the main structural feature. A non-linear behaviour for the decreasing lattice constants of the pseudo-isotypic series from La3NS3 to Dy3NS3 concerning the a- and c-axes is observed along with the lanthanoid contraction caused by the diminishing coordination sphere of (M1)3+ (CN = 7) and (M3) 3+ (CN = 7) moving from the light to the heavier lanthanides. Curie-Weiss-type magnetic behaviour for Dy3NS3 with μeff = 10.3(1) μB for DyN1/3S corresponding to a 6H15/2 groundstate for Dy3+ at higher temperatures and antiferromagnetic ordering of the Dy3+ moments below 5 K is observed.
- Lissner, Falk,Meyer, Monika,Kremer, Reinhard K.,Schleid, Thomas
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p. 1995 - 2002
(2008/10/09)
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- Reduced lanthanum halides with Ge as interstitials: La2I 2Ge, La2I2Ge2, La3Cl 2Ge3, La3Br2Ge3, La 3I3Ge, La
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The title compounds were synthesized from La, LaX3 (X = Cl, Br and I) and Ge under Ar atmosphere at temperatures 860-1200°C. Their structures are characterized by Ge-centered La6 octahedra or trigonal prisms. Ge atoms form planar zig
- Mattausch, Hansjuergen,Zheng, Chong,Ryazanov, Mikhail,Simon, Arndt
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p. 302 - 308
(2008/10/09)
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- La4Br2Al5 and Ce4Br 2Ga5: Three-dimensional Metal Networks Embedded in Condensed Ln6 Trigonal Prisms
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La4Br2Al5 and Ce4Br 2Ga5 are metal-rich and feature Al or Ga centered Ln 6 (Ln = La, Ce) trigonal prisms. The packing of these prisms is unique and characterizes a new variation in reduced rare-earth halides. The prisms fuse into dimeric units which in turn form rectangles parallel to the a-b plane. They then stack in the [0 0 1] direction, creating channels along the c-axis. The halides occupy these channels, while Al or Ga atoms join to a three-connected, three-dimensional network encircling these channels. The title compounds represent a new structure type, crystallizing in the space group Cmmm (No. 65) with lattice constants a = 16.115(3) and 15.796(3) A, b = 17.206(3) and 16.795(3), c = 4.3280(9) and 4.2344(8) A, respectively for La4Br2Al5 and Ce4Br 2Ga5. An isostructural, however nonstoichiometric and disordered phase La4.15Br2Ga4.69 also exists with a = 15.902(1) A, b = 17.034(1) A, and 4.2612(3) A. Computational analysis reveals that they belong to the class of reduced valence rare-earth halides. However, because of the extended interaction between Ln and M, the conduction band of these compounds is partially occupied. Conductivity and magnetic susceptibility measurements confirm the metallic nature of these compounds, and reveal Cerium to be trivalent as expected.
- Zheng, Chong,Mattausch, Hansjuergen,Oeckler, Oliver,Nuss, Juergen,Simon, Arndt
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p. 2229 - 2235
(2008/10/09)
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- La3X3Z - Compounds with Condensed La6Z Octahedra Helically Connected in Three Dimensions
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The subhalides La3X3Z (X=Br, I, Z=Si, P, As, Sb, C2) were synthesized from stoichiometric mixtures of La, LaX3 and Z under Ar atmosphere in sealed Ta ampoules at 950°C to 1200°C for 3-30 days. La3X3Z (X=Br, I, Z=Si, P, As, Sb) is isostructural to Gd3Cl3C (Z=8, space group I4132, No. 214) which can be described as a defect NaCl type. This structure is characterized by the main group element Z centered octahedra propagating helically in three dimensions. The lattice constants a are 12.163(3), 12.4267(5), 12.533(1) and 12.780(1) ? for La3Br3Si, La3I3P, La3I3As and La3I3Sb, respectively. The excess electrons in the La dxy conduction band lead to a metallic behavior for these compounds. La3Br3Si undergoes a metal-insulator transition at 36 K which is attributed to a structural change. La3Br3C2 crystallizes in a different space group C2221 (No. 20), Z=16, a=11.5330(6) ?, b=17.0698(6) ?, c=17.0540(8) ?. The C2 units center highly distorted La octahedra. This structure, however, is related to the above I4132 structure in that the edge-sharingLa6 octahedra fill space in a similar way. This compound is a semicondu ctor (electrical gap Eg=0.02 eV) and its conducting property can be understood from the closed-shell electron configuration of (La(3+))3(Br(-))3(C2)(6-).
- Zheng, Chong,Oeckler, Oliver,Mattausch, Hansjuergen,Simon, Arndt
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- Enthalpy of phase transitions and heat capacity of stoichiometric compounds in LaBr3-MBr systems (M = K, Rb, Cs)
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Molar enthalpies of solid-solid and solid-liquid phase transitions of the LaBr3, K2LaBr5, Rb2LaBr5, Rb3LaBr6 and Cs3LaBr6 compounds were determined by differential scanning calorimetry. K2LaBr5 and Rb2LaBr5 exist at ambient temperature and melt congruently at 875 and 864 K, respectively, with corresponding enthalpies of 81.5 and 77.2 kJ mol-1. Rb3LaBr6 and Cs3LaBr6 are the only 3:1 compounds existing in the investigated systems. The first one forms from RbBr and Rb2LaBr5 at 700 K with an enthalpy of 44.0 kJ mol-1 and melts congruently at 940 K with an enthalpy of 46.7 kJ mol-1. The second one exists at room temperature, undergoes a solid-solid phase transition at 725 K with an enthalpy of 9.0 kJ mol-1 and melts congruently at 1013 K with an enthalpy of 57.6 kJ mol-1. Two other compounds existing in the CsBr-based systems (Cs2LaBr5 and CsLa2Br7) decompose peritectically at 765 and 828 K, respectively. The heat capacities of the above compounds in the solid as well as in the liquid phase were determined by differential scanning calorimetry. A special method - `step method' developed by SETARAM was applied in these measurements. The heat capacity experimental data were fitted by a polynomial temperature dependence.
- Rycerz,Gaune-Escard
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p. 355 - 363
(2008/10/08)
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- Layered lanthanum carbide halide superconductors La2C2(X,X′)2 (X,X′ = Cl, Br, I): Neutron powder diffraction characterization and electronic properties
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The superconducting properties of La2C2(X, X′)2(X, X′ = Cl, Br, I) are investigated. Three different samples of La2C2Br2, which are obtained under different synthesis conditions, show superconductivity at 7.03(5) K. La2C2I2 (Tc≈1.7 K) exhibits slightly different transition temperatures for differently prepared samples. A total of five samples of La2C2(X, X′)2 were investigated by high resolution neutron powder diffraction from room temperature to 1.5 K. Rietveld refinements yield the structural parameters, in particular of the C atoms. These allow us to follow in detail the variation of the interatomic distance in the C2 group. On the basis of the low temperature structural parameters, extended Hueckel band structure calculations were performed and a band of low dispersion along the Γ-N direction in the Brillouin zone was identified. We discuss correlations of structural and electronic properties with the superconducting transition temperatures of the La2C2(X, X′)2 phases.
- Ahn, Kyungsoo,Gibson, Brendan J.,Kremer, Reinhard K.,Mattausch, Hansjuergen,Stolovits, Andres,Simon, Arndt
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p. 5446 - 5453
(2007/10/03)
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- Zintl anions of silicon in the halides La3Cl2Si3 and La6Br3Si7
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La3Cl2Si3 and La6Br3Si7 are prepared at temperatures of around 950 °C from LaX3 (X = Cl, Br), La metal and Si as starting materials. La3Cl2Si3 crystallizes in C2/m with a = 1802(3), b = 420.6(4), c = 1058(2) pm, β= 97.9(2)°, and La6Br3Si7 in Pmmn mit a = 1686.9(2), b = 412.93(11), c = 1185.2(1) pm. In both compounds the Si atoms are located in trigonal prisms of La atoms, which are connected through common triangular and rectangular faces to form layers. The bromine atoms connect the metal atom double layers. In La3Cl2Si3 the Si atoms form zig-zag chains, in La6Br3Si7 chains build up from 1∞-connected Si12 rings. Both compounds are metallic conductors.
- Mattausch, Hansjuergen,Oeckler, Oliver,Simon, Arndt
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p. 297 - 301
(2008/10/08)
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- Planar B4 rhomboids: The rare earth boride halides RE4X5B4
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The new compounds RE4X5B4 (RE = La, Ce, Pr, Gd and X = Br, I) and RE4I5B2C (RE = La, Ce) are prepared via the reaction of RE metal, REX3 and B, or B and C at temperatures 1670 ≥ T ≥ 1270 K in welded tantalum ampoules. Chains of interconnected B4 rhomboids are the characteristic features of the crystal structures. According to band structure calculations, the compounds are one-dimensional metals which undergo a gradual metal-to-semiconductor transition at low temperature as experimentally indicated by the steep inrease of electrical resistivity.
- Mattausch,Simon,Felser
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p. 9951 - 9957
(2007/10/03)
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- Formation enthalpies of the MBr-LaBr3 liquid mixtures (M = Li, Na, K, Rb, Cs)
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Molar enthalpies of mixing of the LiBr-LaBr3, NaBr-LaBr3, KBr-LaBr3, RbBr-LaBr3 and CsBr-LaBr3 systems have been measured with a Calvet-type high-temperature microcalorimeter. The enthalpies decrease gradually from -0.67 kJ mol-1 for the lithium system through -4.32, -10.73 and -14.97 kJ mol-1 for the sodium, potassium, and rubidium systems to -16.81 kJ mol-1 for that of cesium at the composition of the 3 MBr·LaBr3 compound. The results have been discussed in terms of the conformal solution theory of Davis as well as in terms of relative ionic potentials.
- Gaune-Escard, Marcelle,Bogacz, Aleksander,Rycerz, Leszek,Szczepaniak, Wlodzimierz
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- Lanthanum, Gadolinium, and Yttrium Oxobromides
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The conditions for the solid-state synthesis of lanthanum, gadolinium, and yttrium oxobromides are studied. The procedure of synthesis of these compounds is improved. Simple and mixed-cation lanthanum, gadolinium, and yttrium oxobromides are prepared and their thermal properties are studied.
- Suponitskii, Yu. L.
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p. 899 - 903
(2008/10/08)
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- COMPLEXES OF YTTRIUM AND LANTHANIDE BROMIDES WITH 4-N-(2'-HYDROXYBENZYLIDENE)AMINOANTIPYRINEY
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Ten new complexes of bromides of yttrium and lanthanides with 4-N-(2'-hydroxybenzylidene)aminoantipyrine (HBAAP) having the formula [Ln(HBAAP)2Br2]Br, where Ln = Y, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho and Er have been prepared and characterized. Molar conductance studies indicate 1:1 electrolytic behaviour for these complexes. Their infrared spectra show that HBAAP acts as a neutral tridentate ligand coordinatin throuhg the carbonyl oxzgen, azomethine nitrogen and phenolic oxygen. Electronic spectra showthe week covalent character in the metal-ligand bond. Thermogravimetric studies indicate that these complexes are stable up to about 170.degree .C and undergo decomposition in two stages forming the respective metal bromides as the final products.
- Joseph, M.,Nair, M. K. M.,Radhakrishnan, P. K.
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p. 1331 - 1344
(2008/10/09)
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- Kinetics and mechanism of the thermal decomposition of lanthanum complexes of 4-N-(4'-antipyrylmethylidene) aminoantipyrine
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The kinetics and mechanism of the thermal decomposition of perchlorate, nitrate, chloride, bromide, and iodide complexes of lanthanum with the Schiff base 4-N-(4'-antipyrylmethylidene) aminoantipyrine (abbreviated asAA) have been studied by TG and DTG tec
- Nair, M. K. Muraleedharan,Radhakrishnan, P. K.
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p. 141 - 150
(2008/10/09)
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- Thermochemical studies on the systems ABr-LaBr3 (A ≡ Na, K, Rb, Cs)
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The pseudo-binary systems ABr-LaBr3 (A ≡ Na-Cs) were investigated by means of differential thermal analysis and X-ray diffraction of crystal powders. The system NaBr/LaBr3 is eutectic: in all other systems the compounds A2LaBr5(K2PrCl5-type) exist. Additional compounds A3LaBr6, stable only at high temperature, are formed with RbBr and CsBr. They have the elpasolite-structure; modifications, metastable at ambient temperature, crystallize into the K3MoCl6-type. A further high-temperature compound, CsLa2Br7, has the same structure as RbDy2Cl7. The thermodynamic functions of the ternary bromides were determined using solution calorimetry and e.m.f. vs. T measurements in galvanic cells for solid electrolytes. These were then compared with those of the LaCl3 system. The main result is that, except for the halide ion, the A2LaX5 compounds are formed from adjacent compounds in the systems with a resulting gain in lattice enthalpy. All other compounds have less favourable structures: a loss of lattice enthalpy is compensated for by a gain in entropy at sufficiently high temperatures.
- Seifert, Hans J.,Yuan, Yizhong
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p. 135 - 144
(2008/10/08)
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