- Molecular and ionic sublimation of neodymium tribromide polycrystals and single crystals
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The molecular and ionic sublimation of polycrystals and single crystals under Knudsen effusion and Langmuir evaporation conditions is reported. In both sublimation regimes, the sublimation product at 780-1050 K contains neodymium tribromide monomer and dimer molecules, as well as the negative ions NdBr 4 -, Nd2Br 7 -, and Br-. The dimer-to-monomer flux ratio j(Nd2Br 6)/j(NdBr3)is larger in the molecular beam coming out of the effusion hole, while the ratio of the sublimation fluxes of the negative ions, j(Nd2Br 7 - )/j(NdBr 4 - ), is independent of the sublimation conditions. The partial pressures of the neutral components of the vapor have been determined, and the enthalpies and activation energies of sublimation of neodymium tribromide as monomer and dimer molecules and NdBr 4 - and Nd 2Br 7 - ions have been calculated. The equilibrium constants of ion-molecule reactions have been measured, and the enthalpies of these reactions have been determined. Based on these data, values of the thermodynamic properties Δ s H 0(298.15) and Δ f H 0(298.15) are recommended for the monomer and dimer molecules and the NdBr 4 - and Nd2Br 7 - ions.
- Kudin,Butman,Motalov,Nakonechnyi,Kr?mer
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- Phase diagram and electrical conductivity of the AgBr-NdBr3 binary system
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DSC was used to investigate phase equilibrium in the AgBr-NdBr3 system. This binary mixture was characterized as an eutectic system with solid solutions. The eutectic composition and temperature were found to be: x(AgBr) = 0.845 and Teut/
- Kolodziej,Szymanska-Kolodziej,Chojnacka,Rycerz,Gaune-Escard
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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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- Lanthanide(III) halides: Thermodynamic properties and their correlation with crystal structure
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Temperatures and enthalpies of phase transitions of 17 lanthanide(III) halides determined experimentally are reported. Correlations were made between temperature of fusion of lanthanide(III) halides, on the one hand, and enthalpy of fusion, on the other, versus atomic number of lanthanide. According to this classification, the lanthanide(III) halides split into groups, as also do the corresponding crystal structures. A correlation between the crystal structure of lanthanide(III) halides and their respective entropy of fusion (or entropy of fusion + entropy of solid-solid phase transition) was inferred from the aforementioned features. Fusion in those halides with hexagonal, UCl3-type and orthorhombic, PuBr3-type, structures entails an entropy of fusion change (or entropy of fusion + entropy of solid-solid phase transition change) by 50 ± 4 J mol-1 K-1. The homologous entropy change within the group of halides having the rhomboedric, FeCl3-type, structure, is smaller and equals 40 ± 4 J mol-1 K-1. Halides with monoclinic, AlCl3-type, crystal structure constitute a third group associated to an even smaller entropy change upon fusion, only 31 ± 4 J mol-1 K-1. The halides with lower entropies of fusion also have a lower S1300 K - S298 K indicating either a higher degree of order in the liquid or a higher entropy in the solid at room temperatures.
- Rycerz,Gaune-Escard
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p. 167 - 174
(2008/10/09)
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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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- Synthesis, structure and reactivity of tris-, bis- and mono(2,4- dimethylpentadienyl) complexes of neodymium, lanthanum and yttrium
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The tris(2,4-dimethylpentadienyl) complexes [Ln(η5-Me 2C5H5)3] (Ln = Nd, La, Y) are obtained analytically pure by reaction of the tribromides LnBr 3·THF with the potassium compound K(Mesub
- Kunze, Michael R.,Steinborn, Dirk,Merzweiler, Kurt,Wagner, Christoph,Sieler, Joachim,Taube, Rudolf
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p. 1451 - 1463
(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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- Formation enthalpies of MBr-NdBr3 liquid mixtures (M = Li, Na, K, Rb, Cs)
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Molar enthalpies of mixing ΔmixHom, of the LiBr-NdBr3, NaBr-NdBr3, KBr-NdBr3, RbBr-NdBr3, and CsBr-NdBr3 liquid binary systems have been measured with a Calvet-type high-temperature microcalorimeter under argon at 1063 K over the whole composition range. Mixing of the two liquid components was carried out using a break-off ampoule technique. For all the systems, the enthalpies of mixing were negative and their minima (at XNdBr3 ≈ 0.4) were - 0.7, -5.4, -12.4, -17.8 and -20.1 kJ mol-1, respectively. The results have been compared with data previously published for MCl-NdCl3 systems and discussed in terms of possible complex formation.
- Gaune-Escard, Marcelle,Bogacz, Aleksander,Rycerz, Leszek,Szczepaniak, Wlodzimierz
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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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