Sur une nouvelle famille de composes MIIMIVLi2F8 de structure apparentee a celle de la scheelite

Vedrine, A.; Baraduc, L.; Cousseins, J.C.

doi:10.1016/0025-5408(73)90135-9

Cited by 13 publications

(11 citation statements)

References 3 publications

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“…Simple molecular fluorides such as these are uncommon, as only eight of over 50 ternary (M x U y F z ) and quaternary (M w M′ x U y F z ) uranium(IV) structures (M, M′ = NH 4 + , group 1–13 metal ions, Ge 4+ , Sn 2+/4+ , Pb 2+/4+ , Sb 3+/5+ ) currently in the Inorganic Crystal Structure Database (ICSD) feature such distinct uranium environments. The remaining structures all feature corner-, edge-, or face-sharing structures and one- to three-dimensional topologies, most of which are held together by μ 2 bridging fluorides. ,,− One important exception is UF 6 , which sublimes at relatively mild temperature alongside homologue UCl 6 , due to weak van der Waals interactions between discrete octahedral molecules. , …”

Section: Introductionmentioning

confidence: 99%

Electronic, Magnetic, and Theoretical Characterization of (NH₄)₄UF₈, a Simple Molecular Uranium(IV) Fluoride

et al. 2018

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The simple system of tetraammonium octafluorouranate is employed to derive a fundamental understanding of the uranium–fluorine interaction. The structure is composed of isolated molecules, enabling a detailed examination of the U4+ (f 2) ion. Characterization of single-crystals by X-ray diffraction, absorption spectroscopy, and magnetic analysis up to 45 T is combined with extensive theoretical treatment by CASSCF. The influence of different active spaces and representations of the structure is examined in the context of the experimental evidence. The Interacting Quantum Atoms method (IQA) is used to examine the nature of the U–F bond, concluding that there is a non-negligible degree of covalent character (9% of the total bond energy) in [UF8]4−. For the structural and theoretical reasons discussed herein, it is proposed that the structure of (NH4)4UF8 may be appropriately employed as a benchmark compound for future theoretical characterization of U(IV).

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Section: Introductionmentioning

confidence: 99%

Electronic, Magnetic, and Theoretical Characterization of (NH₄)₄UF₈, a Simple Molecular Uranium(IV) Fluoride

et al. 2018

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“…Uranium fluorides are an important group of materials that are fundamental for uranium separation processes, are potential materials for use in long-term nuclear waste storage, and can play a role in the development of new classes of fuel rod assemblies. − Not surprisingly, the binary uranium fluorides, such as UF 4 and UF 6 , have been extensively investigated and are currently being used in a variety of nuclear processes. − In addition, over 20 ternary inorganic uranium fluorides (other than minerals), such as alkali uranium fluorides and some transition metal uranium fluorides (Na 2 UF 6 , Na 3 UF 7 , K 3 UF 7 , CsU 2 F 9 , AuU 2 F 11 ) have been synthesized, and their structures were reported in the literature. − Surprisingly, only a handful of quaternary uranium-containing fluorides, such as CaLi 2 UF 8 , have been reported. , Typically the U 4+ cations in these structures are found in large coordination environments of UF x ( x = 7, 8, 9) polyhedra that lead to the formation of complex structure types. Remarkably, the total number of transition metal-containing uranium fluorides is very small, considering the importance of uranium as an element.…”

Section: Introductionmentioning

confidence: 99%

Application of a Mild Hydrothermal Approach Containing an in Situ Reduction Step to the Growth of Single Crystals of the Quaternary U(IV)-Containing Fluorides Na₄MU₆F₃₀ (M = Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺) Crystal Growth, Structures, and Magnetic Properties

et al. 2014

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A family of rare U(IV)-containing quaternary fluorides, Na4MU6F30 (M = Mn(2+), Co(2+), Ni(2+), Cu(2+), and Zn(2+)), was synthesized in single crystal form via a mild hydrothermal technique utilizing an in situ U(VI) to U(IV) reduction step. The modified hydrothermal route is described, and the conditions to obtain single crystals in high yield are detailed. The crystal structures were determined by single crystal X-ray diffraction. The isostructural fluorides crystallize in a new structure type in the trigonal space group P3̅c1. They exhibit a complex three-dimensional crystal structure consisting of corner- and edge-shared UF9 and MF6 polyhedra. The main building block, a U6F30(6-) group, is arranged to create two distinct hexagonal channels, inside which MF6 octahedra and Na(+) cations are located. The copper-containing member of the series, Na4CuU6F30, is unusual in that the Cu(2+) cation exhibits a rare symmetrical coordination environment consisting of six identical Cu-F bond distances, indicating the lack of the expected Jahn-Teller distortion. Magnetic susceptibility measurements of Na4ZnU6F30 yielded an effective magnetic moment of 3.42 μB for the U(4+) (f(2)) cation in the structure. Measurements of the other members containing magnetic transition-metal cations in addition to U(4+), Na4MU6F30 (M = Mn(2+), Co(2+), Ni(2+), and Cu(2+)) yielded total effective magnetic moments of 10.2, 9.84, 8.87, and 8.52 μB for the Mn-, Co-, Ni-, and Cu-containing materials, respectively. No evidence for long-range magnetic ordering was found down to 2 K. Measurements of the magnetization as a function of applied magnetic field at 2 K for Na4MnU6F30 confirmed that the U(4+) magnetic cation exhibits a nonmagnetic singlet ground state at low temperature. Thermal stability measurements and UV-vis diffuse reflectance spectroscopy are also reported.

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“…The ternary LiF−ThF 4 − CaF 2 phase diagram was calculated based on the assessed subbinary systems (LiF−CaF 2 , LiF−ThF 4 , and CaF 2 −ThF 4 ) according to the Kohler/Toop formalism. The existence of a ternary compound with stoichiometry Li 2 CaThF 8 was reported by Vedrine et al30 and has been considered in this work. In the absence of evidence of any other ternary intermediate compound, this was the only one considered in our assessment.…”

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confidence: 73%

Thermodynamic Investigation of the CaF₂–ThF₄ and the LiF–CaF₂–ThF₄ Systems

et al. 2015

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In this study we present the thermodynamic description of the binary CaF2–ThF4 system and the ternary LiF–CaF2–ThF4 system. In order to describe the general shape of the phase diagram, the phase equilibria of several intermediate compositions of the CaF2–ThF4 system have been measured for the first time in the present work using the DSC technique. These results have been combined with X-ray diffraction studies for the identification of the phases in equilibrium and for the determination of the structure of the CaThF6 compound. Considering all of the novel experimental data, the CaF2–ThF4 system has been assessed for the first time using the Calphad approach. Moreover, the ternary LiF–CaF2–ThF4 phase diagram has been calculated and optimized using the experimental data obtained in this study for the ternary mixtures. The model developed reproduces very well all the measurements performed and correctly predicts the lowest eutectic temperature and composition.

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Sur une nouvelle famille de composes MIIMIVLi2F8 de structure apparentee a celle de la scheelite

Cited by 13 publications

References 3 publications

Electronic, Magnetic, and Theoretical Characterization of (NH₄)₄UF₈, a Simple Molecular Uranium(IV) Fluoride

Electronic, Magnetic, and Theoretical Characterization of (NH₄)₄UF₈, a Simple Molecular Uranium(IV) Fluoride

Application of a Mild Hydrothermal Approach Containing an in Situ Reduction Step to the Growth of Single Crystals of the Quaternary U(IV)-Containing Fluorides Na₄MU₆F₃₀ (M = Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺) Crystal Growth, Structures, and Magnetic Properties

Thermodynamic Investigation of the CaF₂–ThF₄ and the LiF–CaF₂–ThF₄ Systems

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Sur une nouvelle famille de composes MIIMIVLi2F8 de structure apparentee a celle de la scheelite

Cited by 13 publications

References 3 publications

Electronic, Magnetic, and Theoretical Characterization of (NH4)4UF8, a Simple Molecular Uranium(IV) Fluoride

Electronic, Magnetic, and Theoretical Characterization of (NH4)4UF8, a Simple Molecular Uranium(IV) Fluoride

Application of a Mild Hydrothermal Approach Containing an in Situ Reduction Step to the Growth of Single Crystals of the Quaternary U(IV)-Containing Fluorides Na4MU6F30 (M = Mn2+, Co2+, Ni2+, Cu2+, and Zn2+) Crystal Growth, Structures, and Magnetic Properties

Thermodynamic Investigation of the CaF2–ThF4 and the LiF–CaF2–ThF4 Systems

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Electronic, Magnetic, and Theoretical Characterization of (NH₄)₄UF₈, a Simple Molecular Uranium(IV) Fluoride

Electronic, Magnetic, and Theoretical Characterization of (NH₄)₄UF₈, a Simple Molecular Uranium(IV) Fluoride

Application of a Mild Hydrothermal Approach Containing an in Situ Reduction Step to the Growth of Single Crystals of the Quaternary U(IV)-Containing Fluorides Na₄MU₆F₃₀ (M = Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺) Crystal Growth, Structures, and Magnetic Properties

Thermodynamic Investigation of the CaF₂–ThF₄ and the LiF–CaF₂–ThF₄ Systems