13572-98-0Relevant articles and documents
Giant Negative Magnetoresistance in GdI2: Prediction and Realization
Felser,Ahn,Kremer,Seshadri,Simon
, p. 19 - 25 (1999)
The electronic structure of the layered d1 compound GdI2 has been examined systematically in view of its relation to other layered d1 systems including superconducting and isostructural 2H-TaS2 and 2H-NbSe2. A van Hove type instability is evident in suitable representations of the Fermi surface. The presence of the half-filled and magnetic 4f level should preclude the possibility of superconductivity. Instead GdI2 orders ferromagnetically at 290(5) K and displays large negative magnetoresistance ≈70% at 7 T close to room temperature. This finding provides support to the idea that materials can be searched rationally for interesting properties through high level electronic structure calculations.
Gd10I16(C2)2 and Gd10Br15B2/Tb10Br15B 2 cluster compounds with M10 twin octahedra
Mattausch, Hansju?rgen,Warkentin, Eberhard,Oeckler, Oliver,Simon, Arndt
, p. 2117 - 2124 (2000)
The compound Gd10I16(C2)2 can be prepared from Gd metal, GdI3 and C at 950 °C. It crystallizes in P1? with a = 10.463(4) A?, b = 16.945(6) A?, c = 11.220(4) A?, α = 99.15(3)°, β = 92.68(3)° und γ = 88.06(3)°. Gd10Br15B2 is formed between 900 und 950 °C, Tb10Br15B2 between 900 und 930 °C from stoichiometric amounts of the rare earth metals, tribromide and boron. Both compounds crystallize in the space group P1? for Gd10Br15B2 with a = 8.984(2) A?, b = 9.816(2) A?, c = 10.552(5) A?, α = 91.14(3)°, β = 114.61(3)° and γ = 110.94(3)° and for Tb10Br15B2 with a = 8.939(4) A?, b = 9.788(3) A?, c = 10.502(2) A?, α = 91.19(3)°, β = 114.51(3)° and γ = 111.10(2)°. In the crystal structures of all three compounds the rare earth metals form edge-shared Ln10 twin octahedra. In Gd10I16(C2)2 the Gd octahedra are centered with C2 groups (dC-C = 1.43(7) A?). In Ln10Br15B2 (Ln = Gd, Tb) the octahedra contain single boron atoms. The clusters are connected through halide atoms to chains [Ln10(Z)2Xi4Xi-i 4/2Xi-a2]. Adjacent chains are fused threedimensionally via Ii-a2Ii-a6 for the Gd iodide carbide and via Bri-i2/2Bri-a6 for the bromide borides of Gd und Tb. It is interesting to see an identical pattern of connection between the chains for the reduced oxomolybdates, e. g. PbMo5O8.
From an impurity to the pure compound - An electron microscopy study
Kienle,Lukachuk,Duppel,Mattausch,Simon
, p. 1708 - 1712 (2007)
The power of electron microscopy techniques for the determination of structure and composition of marginal byproducts is demonstrated for rare earth metal cluster compounds. Small amounts of the new phase Gd4GaI 6 in samples with the nominal composition Gd7GaI 12 could only be identified by a combined approach of EDX, electron diffraction and HRTEM. The structure of Gd4GaI6 can be assigned to the Y4BBr6-type containing chains of Gd 6 octahedra which are centered by Ga atoms. The results of the electron microscopy study initiated the synthesis of homogeneous samples of the new compound Gd4GaI6 by applying the correct ratio of the starting materials.
Structural characterization of methanol substituted lanthanum halides
Boyle, Timothy J.,Ottley, Leigh Anna M.,Alam, Todd M.,Rodriguez, Mark A.,Yang, Pin,Mcintyre, Sarah K.
, p. 1784 - 1795 (2010/07/03)
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.
New layered germanide halides RE2GeX2 (RE = Y, Gd; X = Br, I)
Lukachuk, Mar'yana,Kremer, Reinhard K.,Mattausch, Hansjuergen,Simon, Arndt
, p. 3231 - 3235 (2008/10/09)
The title compounds were synthesized from RE, REX3, and Ge under an Ar atmosphere at 1200-1370 K. Y2GeI2 and Gd 2GeI2 crystallize in space group R3m with lattice constants a = 4.2135(3) and 4.2527(1) A and c = 31.480(2) and 31.657(1) A, respectively. Gd2GeBr2 crystallizes in two modifications, the 1T-type (space group P3m1; a = 4.1668(2) A, c = 9.8173(6) A) and the 3R-type (space group R3m; a = 4.1442(9) A, c = 29.487(7) A). The structural motifs of RE2GeX2 compounds are Ge-centered slightly distorted RE6 octahedra connected via their common edges and extending in the a and b directions. The resulting close-packed double layers are separated by halogen atoms. The electrical resistivity measurements revealed semiconductor behavior for Y 2GeI2 and Gd2GeI2 and a metal-semiconductor transition for 1T-Gd2GeBr2. Magnetic susceptibility and heat capacity measurements show long-range magnetic ordering for Gd2GeI2 and 1T-Gd2GeBr2 at ～15 and ～13 K, respectively.
