Study of the dehydration process of uranyl difluoride hydrates stable under usual conditions of temperature, pressure and atmospheric moisture

Morato, F.; Fulconis, J.M.; Rouquérol, F.; Fourcade, R.

doi:10.1016/s0022-1139(98)00214-0

Cited by 7 publications

(16 citation statements)

References 5 publications

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“…Uranyl fluoride forms small (<1 μ m) particulates from this reaction, which were subsequently collected on a series of silicon plates. The material was baked under a steady flow of 10 mL/s N 2 at 150 °C for 18 h, a procedure which has been shown to produce anhydrous uranyl fluoride without decomposing the crystal structure 2,29 . The sample was further exposed to vacuum and baked at 150 °C in the beamline for several hours prior to data collection on ARCS to drive off additional surface-adsorbed water.…”

Section: Methodsmentioning

confidence: 99%

“…The existence of transient O yl –H bonds increases the effective mass of the oscillator by 1 amu. Considering most uranyl ions are not near water molecules (as required by previous thermal gravimetric measurements), the fundamental oscillation frequency at 112 meV represents unperturbed uranyl ions 2 . Adding a nearby H-bonded water molecule shifts the frequency bycompared to the measured value of 109.0 meV.…”

Section: Water Couplingmentioning

confidence: 99%

“…UO 2 F 2 is comprised of layers of uranyl ions hexagonally coordinated by fluoride ligands. At ambient conditions anhydrous uranyl fluoride is a hygroscopic powder that can undergo a hydration reaction resulting in uranyl fluoride hydrate 2 . The transition to the hydrated state can be reversed through annealing under vacuum conditions at 115 °C 1 .…”

Section: Introductionmentioning

confidence: 99%

“…The transition to the hydrated state can be reversed through annealing under vacuum conditions at 115 °C 1 . The exact locations of retained water molecules in the anhydrous structure were heretofore unknown, but the appearance of stacking disorder in x-ray and neutron diffraction patterns offered tantalizing hints of interlayer waters 2,3 .…”

Section: Introductionmentioning

confidence: 99%

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Analysis of Water Coupling in Inelastic Neutron Spectra of Uranyl Fluoride

Miskowiec

Niedziela

Kirkegaard

et al. 2019

Sci Rep

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Inelastic neutron scattering (INS) is uniquely sensitive to hydrogen due to its comparatively large thermal neutron scattering cross-section (82 b). Consequently, the inclusion of water in real samples presents significant challenges to INS data analysis due directly to the scattering strength of hydrogen. Here, we investigate uranyl fluoride (UO 2 F 2 ) with inelastic neutron scattering. UO 2 F 2 is the hydrolysis product of uranium hexafluoride (UF 6 ), and is a hygroscopic, uranyl-ion containing particulate. Raman spectral signatures are commonly used for inferential understanding of the chemical environment for the uranyl ion in UO 2 F 2 , but no direct measurement of the influence of absorbed water molecules on the overall lattice dynamics has been performed until now. To deconvolute the influence of waters on the observed INS spectra, we use density functional theory with full spectral modeling to separate lattice motion from water coupling. In particular, we present a careful and novel analysis of the Q-dependent Debye–Waller factor, allowing us to separate spectral contributions by mass, which reveals preferential water coupling to the uranyl stretching vibrations. Coupled with the detailed partial phonon densities of states calculated via DFT, we infer the probable adsorption locations of interlayer waters. We explain that a common spectral feature in Raman spectra of uranyl fluoride originates from the interaction of water molecules with the uranyl ion based on this analysis. The Debye–Waller analysis is applicable to all INS spectra and could be used to identify light element contributions in other systems.

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Section: Methodsmentioning

confidence: 99%

Section: Water Couplingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Analysis of Water Coupling in Inelastic Neutron Spectra of Uranyl Fluoride

Miskowiec

Niedziela

Kirkegaard

et al. 2019

Sci Rep

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“…[11][12] The crystal structure is highly dependent on the levels of hydration and various related phases include: α UO2F2 •1.5H2O, β UO2F2 •1.5H2O, and UO2F2 •2H2O. [13][14] Thus far, only the anhydrous (UO2F2) and uranyl fluoride sesquihydrate (UO2F2 •1.57H2O) crystal structures have been characterized by neutron diffraction with the fluorine, oxygen, and uranium atom positions determined. [15][16] Based on the known structural information and the high abundance of 19 F, uranyl fluoride sesquihydrate is well-suited for a benchmarking study for a combined MAS NMR and GIPAW analysis.…”

Section: Introductionmentioning

confidence: 99%

Investigations of Uranyl Fluoride Sesquihydrate (UO₂F₂·1.57H₂O): Combining ¹⁹F Solid-State MAS NMR Spectroscopy and GIPAW Chemical Shift Calculations

et al. 2018

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High-resolution F magic-angle spinning (MAS) NMR spectra were obtained for the uranium-bearing solid uranyl fluoride sesquihydrate (UOF·1.57HO). While there are seven distinct crystallographic fluorine sites, the F NMR spectrum reveals six peaks at -33.3, 9.1, 25.7, 33.0, 39.0, and 48.2 ppm, with the peak at 33.0 ppm twice the intensity of all the others and therefore corresponding to two sites. To assign the peaks in the experimental spectra to crystallographic sites,F chemical shifts were calculated using the gauge including projector augmented waves (GIPAW) plane-wave pseudopotential approach for a DFT-optimized crystal structure. The peak assignments from DFT are consistent with two-dimensional double-quantum F MAS NMR experiments.

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Structural Phase Transitions and Water Dynamics in Uranyl Fluoride Hydrates

Miskowiec

Kirkegaard

Huq³

et al. 2015

J. Phys. Chem. A

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We report a novel production method for uranium oxyfluoride [(UO2)7F14(H2O)7]·4H2O, referred to as structure D. Structure D is produced as a product of hydrating anhydrous uranyl fluoride, UO2F2, through the gas phase at ambient temperatures followed by desiccation by equilibration with a dry environment. We follow the structure of [(UO2)7F14(H2O)7]·4H2O through an intermediate, liquid-like phase, wherein the coordination number of the uranyl ion is reduced to 5 (from 6 in the anhydrous structure), and a water molecule binds as an equatorial ligand to the uranyl ion. Quasielastic neutron scattering results compare well with previous measurements of mineral hydrates. The two groups of structurally distinct water molecules in D perform restricted motion on a length scale commensurate with the O-H bond (r = 0.92 Å). The more tightly bound equatorial ligand waters rotate slower (Dr = 2.2 ps(-1)) than their hydrogen-bonded partners (Dr = 28.7 ps(-1)).

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Study of the dehydration process of uranyl difluoride hydrates stable under usual conditions of temperature, pressure and atmospheric moisture

Cited by 7 publications

References 5 publications

Analysis of Water Coupling in Inelastic Neutron Spectra of Uranyl Fluoride

Analysis of Water Coupling in Inelastic Neutron Spectra of Uranyl Fluoride

Investigations of Uranyl Fluoride Sesquihydrate (UO₂F₂·1.57H₂O): Combining ¹⁹F Solid-State MAS NMR Spectroscopy and GIPAW Chemical Shift Calculations

Structural Phase Transitions and Water Dynamics in Uranyl Fluoride Hydrates

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Study of the dehydration process of uranyl difluoride hydrates stable under usual conditions of temperature, pressure and atmospheric moisture

Cited by 7 publications

References 5 publications

Analysis of Water Coupling in Inelastic Neutron Spectra of Uranyl Fluoride

Analysis of Water Coupling in Inelastic Neutron Spectra of Uranyl Fluoride

Investigations of Uranyl Fluoride Sesquihydrate (UO2F2·1.57H2O): Combining 19F Solid-State MAS NMR Spectroscopy and GIPAW Chemical Shift Calculations

Structural Phase Transitions and Water Dynamics in Uranyl Fluoride Hydrates

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About

Investigations of Uranyl Fluoride Sesquihydrate (UO₂F₂·1.57H₂O): Combining ¹⁹F Solid-State MAS NMR Spectroscopy and GIPAW Chemical Shift Calculations