- Insight into the Crystalline Structure of ThF4 with the Combined Use of Neutron Diffraction, 19F Magic-Angle Spinning-NMR, and Density Functional Theory Calculations
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Because of its sensitivity to the atomic scale environment, solid-state NMR offers new perspectives in terms of structural characterization, especially when applied jointly with first-principles calculations. Particularly, challenging is the study of actinide-based materials because of the electronic complexity of the actinide cations and to the hazards due to their radioactivity. Consequently, very few studies have been published in this subfield. In the present paper, we report a joint experimental-theoretical analysis of thorium tetrafluoride, ThF4, containing a closed-shell actinide (5f0) cation. Its crystalline structure has been revisited in the present work using powder neutron diffraction experiments. The 19F NMR parameters of the seven F crystallographic sites have been modeled using an empirical superposition model, periodic first-principles calculations, and a cluster-based all-electron approach. On the basis of the atomic position optimized structure, a complete and unambiguous assignment of the 19F NMR resonances to the F sites has been obtained.
- Martel, Laura,Capelli, Elisa,Body, Monique,Klipfel, Marco,Bene?, Ondrej,Maksoud, Louis,Raison, Phillipe E.,Suard, Emmanuelle,Visscher, Lucas,Bessada, Catherine,Legein, Christophe,Charpentier, Thibault,Kovács, Attila
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- INFRARED-TRANSPARENT GLASSES DERIVED FROM THE FLUORIDES OF ZIRCONIUM, THORIUM, AN BARIUM.
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Glasses consisting solely of high-purity ZrF//4, ThF//4, and BaF//2 have been synthesized using reactive atmosphere processing (RAP) techniques. RAP of the individual components and molten material with anhydrous HF and CCl//4 is described. The glass molds easily at 312 degree C and 1920 psi with a high-fidelity replication of the die surface. The glass is water-insoluble, unusually hard and strong, and continuously transparent from 0. 3 to 7 mu m.
- Robinson,Pastor,Turk,Devor,Braunstein,Braunstein
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- Thorium Compounds with Bonds to Sulfur or Selenium: Synthesis, Structure, and Thermolysis
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Thorium chalcogenolates Th(ER)4 (E = S, Se; R = Ph, C6F5) form pyridine complexes with a variety of coordination numbers. Four compounds, (py)4Th(SPh)4, (py)3Th(SePh)4, (py)3Th(SC6F5)4, and (py)4Th(SeC6F5)4, have been isolated and characterized by spectroscopic methods and low-temperature single crystal X-ray diffraction. Two of the products, (py)4Th(SPh)4 and (py)4Th(SeC6F5)4, have classic eight coordinate A4B4 square-antiprism geometries. The SePh compound is the only seven coordinate (4Se, 3N) product, and the fluorinated thiolate is distinctive in that the structure contains two dative interactions between Th and fluoride, to give a nine coordinate (3N, 4S, 2F) structure. The EPh compounds decompose thermally to give ThE2 and EPh2, while the fluorinated compounds give primarily ThF4, E2(C6F5)2, and E(C6F5)2.
- Rehe, David,Kornienko, Anna Y.,Emge, Thomas J.,Brennan, John G.
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- Raman scattering study of the orthorhombic-to-tetragonal phase transition of a Li3ThF7 crystal
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Raman spectroscopy was used to study pulled Li3ThF7 single crystals between 298 and 403 K, using six special backscattering geometries. The observed Raman bands were very broad, owing to the disorder related to the statistical occupancy of the lithium sites (with a 3/4 probability). In spite of this, the symmetry rules are well respected assuming an average model with four lithium ions per chemical formula. The spectral evolutions show a structural phase transition occurring at 368 K. After peak deconvolution, we were able to determine and attribute most of the Raman modes corresponding to each phase. The results are compatible with the proposed orthorhombic (Ccca) to tetragonal (P4/ncc) structural phase transition, whose ferroelastic nature would be responsible for the appearance of an ordered microcracking pattern in this crystal. 1999 The American Physical Society.
- Oliveira,Gesland,Pimenta,Moreira
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- Decomposition Pressure and Thermodynamic Stability of Thorium Oxyfluoride
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The decomposition pressure of the oxyfluoride-phase ThOF2(s) was measured by the torsion-effusion method over the range 1100-1250 K.The material vaporizes incongruently to yield ThF4(g) and ThO2(s).Vapor composition was verified by mass spectrometry and vapor molecular weight measurements.A small effusion orifice-area dependence indicates a slight kinetic barrier to the incongruent vaporization process.Derived equilibrium data show that ThOF2(s) is only marginally stable, with a Gibbs energy of formation of about 8 kJ mol-1 from ThF4(s) and ThO2(s).
- Lau, K. H.,Hildenbrand, D. L.
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- Synthesis and nanoscale characterization of (NH4) 4ThF8 and ThNF
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Synthesis of (NH4)4ThF8 by a solid state reaction of ThO2 and NH4HF2 and the formation of ThNF by ammonolysis of (NH4)4ThF8 and ThF4 under differ
- Silva, G.W. Chinthaka,Yeamans, Charles B.,Cerefice, Gary S.,Sattelberger, Alfred P.,Czerwinski, Kenneth R.
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- Synthetic Strategies for the Synthesis of Ternary Uranium(IV) and Thorium(IV) Fluorides
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A series of new U(IV) and Th(IV) fluorides, Na7U6F31 (1), NaUF5 (2), NaU2F9 (3), KTh2F9 (4), NaTh2F9 (5), (H3O)Th3F13
- Klepov, Vladislav V.,Felder, Justin B.,Zur Loye, Hans-Conrad
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- Development of a YF3:ThF4 membrane for the possibility of determining fluoride
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Preparation of yttrium substituted thorium fluoride (YTF) solid solution, YxTh1?xF4?x (x = 0 – 0.15) by fluorinating a stoichiometric ratio of yttria (Y2O3) and thoria (ThO2) with ammonium hydrogen difluoride (NH4HF2) was acheived. The maximum solubility of YF3 in ThF4 was observed to be 15 mol %. All three compositions of YxTh1?xF4?x (x = 0 – 0.15) solid solution showed an enhanced ionic conductivity over ThF4. 5 mol % yttrium substituted ThF4 (5-YTF) had the highest ionic conductivity, almost 2 orders higher than ThF4. The F? ion selective electrode was designed and tested for estimation of fluoride ion in solution (10?1M to 10?5 M). 5-YTF had the highest sensitivity of 40.0 ± 4 mV/decade in the linear range of 10?1 M to 10?4 M. All the three sensors compositions 5, 10 and 15-YTF have sub Nerstian behavior which is attributed to strong OH? ion interefenece.The results were compared with commercial fluoride ISE (Eu: LaF3).
- Gnanasekar, K. I.,Jayaraman, V.,Lakshmi K, Usha,Lakshmigandhan, I.,Ravindranath, Nair Afijith
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- Stabilization of Th3+ ions into mixed-valence thorium fluoride
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The unusual oxidation state 3 of the thorium has been stabilized into a lithium containing non-stoichiometric mixed-valence (III/IV) thorium fluorinated phase with formula Li2xTh12F50 (05.5Ce 12F50 one, the structure of which has been determined from the combined single-crystal X-ray diffraction and high resolution synchrotron powder diffraction. In these phases, the Li+ ions can be divided into two groups and are located either in locked positions or in open channels of the three dimensional framework. The amount of Li+ ions in open channels can be variable, so that the afore mentioned single phase may be considered as an insertion compound. The Li+ insertion is accompanied by the simultaneous reduction of a part of the Th4 ions, resulting in a mixed-valence III/IV thorium fluoride. The electrochemical insertion of Li+ ions into the open channels of the host matrix has been carried out at 60 °C, using an alkylcarbonate PCLiClO4 1 M electrolyte. The Li+ and Th3 contents, both in the starting composition and the Li+ inserted ones, were investigated by high resolution solid state 7Li NMR and EPR, respectively.
- Dubois, Marc,Dieudonn, Belto,Mesbah, Adel,Bonnet, Pierre,El-Ghozzi, Malika,Renaudin, Guillaume,Avignant, Daniel
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- Joint solubility of PuF3 and CeF3 in ternary melts of lithium, thorium, and uranium fluorides
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Joint solubility of PuF3 and CeF3 in melts of the molar composition 78LiF-7ThF4-15UF4 and 72.5LiF-7ThF4-20.5UF4 in the temperature range 550°-800°C was studied. Anhydrous PuF3 and CeF3 spiked with 144Ce, and also anhydrous ThF4 were synthesized. Isothermal saturation method was used for studying the solubility of pressed PuF3 and CeF3 pellets in these melts in an inert (argon) atmosphere. The dependence of the joint solubility of PuF3 and CeF3 on the melt temperature was determined.
- Lizin, A. A.,Tomilin, S. V.,Osipenko, A. G.,Kormilitsyn, M. V.,Nezgovorov, N. Yu.,Ignat'Ev, V. V.
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- NanMTh6F30: A Large Family of Quaternary Thorium Fluorides
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Recently we reported the synthesis, crystal structures, and magnetic properties of compounds in the NanMU6F30 series, where n = 4, 3 and where M is a divalent or trivalent metal cation, respectively. In this article we advance our investigation of this structure type by expanding it to the thorium-containing compounds NanMTh6F30, where n = 3 in the case of MIII = Al, Sc, Ti, V, Cr, Fe, Ga, In, n = 4 when MII = Mg, Mn, Co, Ni, Cu, Zn, and n varies from 3.87 to 4.39 when the M site is partially occupied by a trivalent rare-earth element. Magnetic properties of the compounds containing magnetic ions M = Ti3+, V3+, Cr3+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+ were studied to demonstrate that the substitution of Th(IV) for U(IV) prevents the magnetic ions from coupling magnetically and, therefore, they exhibit simple paramagnetic behavior.
- Klepov, Vladislav V.,Morrison, Gregory,Loye, Hans-Conrad Zur
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- Synthesis of UF4 and ThF4 by HF gas fluorination and re-determination of the UF4 melting point
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Basic thermodynamic and electrochemical data of pure actinide fluorides and their mixtures are required for the design and safety assessment of any presently studied molten salt reactor concept based on molten fluoride salt fuel. Since the actinide fluorides are usually not produced commercially, they have to be prepared from the available input materials, typically oxides. In this work, a specially designed facility for synthesis of pure actinide fluorides using pure HF gas is described, as well as a complete procedure of synthesis and characterisation of pure UF4 and ThF4. The fluorination installation consists of a glove box kept under a purified argon atmosphere, a high temperature horizontal fluorination reactor and a HF supply gas line connected to the glove box. The fluorides were synthesised from high specific surface oxides prepared from the respective oxalates by low temperature calcination. The fluorination was partly stationary and partly in a HF gas flow, based on a heterogeneous powder-gas reaction at high temperatures. The products were characterised by X-ray diffraction and differential scanning calorimetry, which confirmed high purity products obtained by this method. Moreover, the melting point of UF4 was revised using a pure sample and a new value is suggested.
- Sou?ek, Pavel,Bene?, Ond?ej,Claux, Benoit,Capelli, Elisa,Ougier, Michel,Tyrpekl, Václav,Vigier, Jean-Francois,Konings, Rudy J.M.
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- Actinide-silicon multiradical bonding: Infrared spectra and electronic structures of the Si(μ-X)AnF3 (An = Th, U; X = H, F) molecules
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We report a series of Si(μ-X)AnF3 (An = Th, U; X = H, F) complexes with silicon-actinide(IV) single bonds and unexpected multiradical features that form rare triplet silylenes. These bridged molecules have been prepared in microscopic scale through reactions of laser-ablated uranium and thorium atoms with silicon fluorides and identified from infrared spectra in argon and neon matrixes and relativistic quantum chemical calculations. Similar neon matrix experiments for the reactions of uranium with CF4 and CHF3 were carried out for comparison. Our density functional theory calculations show that the Si-U single-bonded species Si(μ-X)UF3 (X = H, F) with U(IV) oxidation state and the quasi-agostic bridge ligand of H or F are most stable among all the isomers, whereas the naively anticipated triple-bonded species XSii - UF3 with U(VI) oxidation state and the double-bonded species XSi?=?UF3 with U(V) oxidation state lie markedly higher in energy. Similar thorium products from reactions with XSiF3 are also found to prefer the Si(μ-X)ThF3 structures with Si-Th single bonds and bridged H or F ligands. High level ab initio wave function theory calculations with the CCSD(T) and CASPT2 methods confirm that the ground states are quintet for Si(μ-X)UF3 and triplet for Si(μ-X)ThF3 with two unpaired electrons on the silylene group. These silicon-bearing molecules as the lowest-energy isomer of XSiAnF3 represent the first silicon-actinide systems with unusual triplet silylenes and Si-An single bonds with multiradical character. They are in dramatic contrast to the uranium-carbon analogs, XCi - UF3, which form triple-bonded singlet ground states with C3v symmetry. The calculated vibrational frequencies of the Si(μ-X)AnF3 complexes agree well with experimental observations. These results accentuate the critical difference of chemical bonding of 3p- and 2p-row main-group elements with actinides. The Lewis electron-pair model and the octet rule break down for these silicon compounds.
- Hu, Han-Shi,Wei, Fan,Wang, Xuefeng,Andrews, Lester,Li, Jun
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p. 1427 - 1437
(2014/02/14)
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- Thorium fluorides ThF, ThF2, ThF3, ThF4, ThF3(F2), and ThF5- characterized by infrared spectra in solid argon and electronic structure and vibrational frequency calculations
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Reactions of laser-ablated Th atoms with F2 produce ThF 4 as the major product based on agreement with matrix spectra recorded of the vapor from the solid at 800-850 °C. Weaker higher-frequency bands at (567.2, 564.8), (575.9, 575.1), and (531.0, 528.4) cm-1 in argon are assigned to ThF, ThF2 and ThF3, ThF 3(F2) on the basis of their chemical behavior upon increasing reagent concentrations, annealing, and irradiation, the use of NF3, OF2, and HF as F-atom sources, and a comparison with frequencies calculated at the DFT/B3LYP and CCSD(T) levels with a large segmented + ECP basis set on Th and the aug-cc-pVTZ basis set on F. An additional broader band at 460 cm-1 is assigned to the ThF 5- anion. The trigonal-bipyramidal ThF5 - anion (calculated electron detachment energy of 7.17 eV) increases at the expense of ThF3(F2) and F3- on full mercury arc irradiation. [ThF3+][F 2-] is shown by calculations to be an ionic complex with a side-bound F2- subunit. This paper reports the first evidence for novel pentacoordinated thorium species including the unique [ThF3+][F2-] ionic radical-ion pair molecule and its electron-capture product, the very stable ThF5 - anion.
- Andrews, Lester,Thanthiriwatte, K. Sahan,Wang, Xuefeng,Dixon, David A.
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p. 8228 - 8233
(2013/08/23)
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- Solubility of UF4, ThF4, and CeF3 in a LiF-NaF-KF melt
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The solubility of UF4, ThF4, and CeF3 in fluoride melt of the composition 45 mol % LiF-12 mol % NaF-43 mol % KF in the temperature interval 773-973 K was determined. The solubility of the fluorides increases with an increase in the melt temperature. The CeF3 solubility in the LiF-NaF-KF system is high: 19.9 mol % at 923 K and 23.3 mol % at 973 K. Experimental data on the solubility of CeF3 (PuF 3 imitator) were compared to the calculated data on the PuF 3 solubility in the LiF-NaF-KF melt. The results showed that CeF3 can be considered as PuF3 imitator in FLINAK melt.
- Seregin,Parshin,Kuznetsov,Ponomarev,Mel'Nikov,Mikhalichenko,Rzheutskii,Manuilov
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p. 491 - 493
(2012/02/05)
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- Infrared spectra and density functional calculations of triplet pnictinidene N÷ThF3, P÷ThF3 and As÷ThF3 molecules
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Thorium atoms react with NF3, PF3, and AsF 3 to produce the first actinide triplet state pnictinidene molecules, N÷ThF3, P÷ThF3, and As÷ThF 3, which are trapped in solid argon and identifie
- Wang, Xuefeng,Andrews, Lester
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p. 9260 - 9265
(2010/02/16)
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- Th2F7[AuF4] - The first fluoroaurate in the system MF4/AuF3
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We observed for the first time single crystals of Th2F7[AuF4] [1] in attempts to synthesize ternary fluoroaurates with tetravalent cations. Concerning to X-Ray-data (Mo-Kα), the light-yellow compound crystallizes tetragonal in the space group I4/mcm (No. 140) with a = 1130.6(1) pm, c = 631.34(7) pm and Z = 4.
- Schmidt,Mueller
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p. 602 - 604
(2008/10/08)
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- Au[AuF4]2 - An unexpected by-product in the system MF4/AuF3 and single crystals of CeF4, a further by-product
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Investigating the system MF4/AuF3 (M = Th4+, Ce4+) we obtained unexpectively Au[AuF4]2 in form of irregular, brown single crystals. It crystallizes monoclinic, space group P21/n (No. 14) with a = 527.21(7) pm, b = 1070.76(10) pm, c = 573.48(7) pm, β= 90.633(14)°, Z = 2, isotypic with Ag[AuF4]2 and Pd[AuF4]2. As a further by-product we obtained for the first time colourless single crystals of CeF4 (monoclinic, C2/c, No. 15, a = 1258.83(8) pm, b = 1062.63(8) pm, c = 822.41(9) pm, β = 126.24(1)°, and Z = 12).
- Schmidt,Müller
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p. 605 - 608
(2008/10/08)
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- Synthesis and characterization of two new ordered crystalline phases close to ThF4-ZrF4 fluoride glasses. I. Crystal structure of ThZrF8
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A study of the ThF4-ZrF4 system reveals the presence, besides an already known vitreous domain, of two stoichiometric crystalline phases. Both are monoclinic, ThZrF8 [space group: P21/c, a= 8.232(1) A, b = 8.510(1) A, c= 16.355(2) A, β= 100.79(1)°; Z= 8], and ThZr2F12 [(non-conventional) space group: 12/m, Im or 12; a = 9.895(2) A, 10.488(2) A, c= 7.856(1) A, β= 90.73(1)°, Z = 4]. Their composition closely corresponds to the limits of the vitreous domain. The unit cell of ThZr2F12 presents close analogies with PrZr2F11 and β-ZrF4 ones. The crystal structure of ThZrF8 is investigated by X-ray diffraction on a single crystal measured on a Siemens P4 diffractometer with MoKα radiation [refinement : Shelxl-93 program, structure solution by direct methods : Shelxs-86 program, R1 = 0.040, wR2 = 0.087 for all reflections]. It corresponds to a 3d-framework of corner-shared ThF9 and ZrF7 polyhedra. The structure of ThZrF8 derives from α-ZrF4 structure-type by a long-range ordering of the ThF9 and ZrF7 polyhedra replacing ZrF8 dodecahedra. The topological transformations between the cationic plane nets of α-ZrF4 and ThZrF8 occur through structural mechanisms (e.g.: anionic bridging) similar to those previously described in the so-called anion-excess ReO3-related phases . Gauthier-Villars.
- Taoudi,Mikou,Laval
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p. 687 - 699
(2008/10/08)
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- Synthesis and characterization of two new ordered crystalline phases close to ThF4-ZrF4 fluoride glasses. II: Crystal structure of ThZr2F12
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ThZr2F12 crystallizes in the non-conventional space group: I2/m with the cell parameters a = 9.895(2) A, 10.488(2) A, c = 7.856(1) A, β = 90.73(1)°, Z= 4. Its crystal structure is investigated by powder X-ray diffraction from reflections recorded on a Siemens D5000 diffractometer with CuKa radiation [Rietveld refinement: Fullprof program; structure solution by direct methods: Shelxs-86 program; RB = 0.039, RP = 0.064, RWP = 0.090]. The crystal structure of ThZr2F12 results from the stacking of alternate sheets of - on one hand, ThF9 tricapped trigonal prisms, - on the other hand, comer- and edge-shared ZrF7 and ZrF8 monocapped and bicapped trigonal prisms. It closely derives from P-ZrF4 and PrZr2F11 structure-types. As these last phases and as ThZrF8, it can be used as a structural model for the homologous fluoride glasses: the analogy between PrZr2F11 and ThZr2F12 structures strongly suggests the similarity of the structure of the fluoride glasses isolated in the LnF3-ZrF4 and ThF4-ZrF4 systems. These glasses appear as structurally the closest to the ideal ZrF4one, with a moderate modifying role for the Th and Ln cations. As already proposed, the presence of similar cationic frameworks in many glass-forming fluorozirconates evidences the strong influence of these frameworks on the existence and the stability of the homologous glasses. Gauthier-Villars.
- Taoudi,Mikou,Laval
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p. 1051 - 1062
(2008/10/08)
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- PHENOMENOLOGICAL COMPARISON OF SOME HEAVY METAL FLUORIDE GLASSES IN WATER ENVIRONMENTS.
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The details of corrosive attack by water on several heavy metal fluoride glasses are given. The glasses studied contained either ZrF//4 or HfF//4 as primary constituents, or, were composed of the fluorides of zinc, thorium, barium and either yttrium or ytterbium. Polished specimens were subjected either to room temperature (RT) liquid water or to 100% relative humidity at room temperature. The degree of surface corrosion was correlated with the preparatory and compositional effects. Thermogravimetric analysis (TGA) was utilized to determine the extent of corrosion as a function of temperature and as a function of time at constant temperature in an atmosphere of RT helium saturated with water.
- Robinson,Drexhage
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p. 1101 - 1112
(2008/10/08)
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