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At least 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Na n MTh 6 F 30 : A Large Family of Quaternary Thorium Fluorides

Recently we reported the synthesis, crystal structures and magnetic properties of compounds in the Na n MU 6 F 30 series, where n = 4 or 3, and where M is a divalent or trivalent metal cation, respectively. Here in this article we advance our investigation of this structure type by expanding it to the thorium containing compounds Na n MTh 6 F 30 , where n = 3 in the case of M III = Al, Sc, Ti, V, Cr, Fe, Ga, or In; n = 4 when MII = Mg, Mn, Co, Ni, Cu, or 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 = Ti 3+ , V 3+ , Cr 3+ , Mn 2+ , Fe 3+ , Co 2+ , Ni 2+ , and Cu 2+ were studied to demonstrate that the substitution of Th(IV) for U(IV) prevents the magnetic ions from coupling magnetically and, therefore, exhibit simple paramagnetic behavior.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Lessons Learned—Fluoride Exposure and Response

Laboratory research can expose workers to a wide variety of chemical hazards. Researchers must not only take personal responsibility for their safety but also inevitably rely on coworkers to also work safely. The foundations for protocols, requirements, and behaviors come from our history and lessons learned from others. For that reason, here, a recent incident is examined in which a researcher suffered hydrofluoric acid (HF) burns while working with an inorganic digestion mixture of aqueous HF (8%) and nitric acid (HNO 3 , 58%). HF education is critical for workers because delays in treatment, improper treatment, and delay of symptoms are all factors in unfavorable outcomes in case reports. Furthermore, while the potential severity of the incident was elevated due to bypassed engineered controls and lack of proper personal protective equipment, only minor injuries were sustained. We discuss the results of a causal analysis of the incident that revealed areas of improvement in protocols, personal protective equipment, and emergency response that could help prevent similar accidents from occurring. We also present simple improvements that anyone can implement to reduce the potential consequences of an accident, based upon our lessons learned.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Electronic, Magnetic, and Theoretical Characterization of (NH 4 ) 4 UF 8 , a Simple Molecular Uranium(IV) Fluoride

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 U 4+ (ƒ 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 (NH 4 ) 4 UF 8 may be appropriately employed as a benchmark compound for future theoretical characterization of U(IV).

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2015

Structural Phase Transitions and Water Dynamics in Uranyl Fluoride Hydrates

We report a novel production method for uranium oxy uoride [(UO 2 ) 7 F 14 (H 2 O) 7 ] 4H 2 O, referred to as structure D. Structure D is produced as a product of hydrating anhydrous uranyl uoride, UO 2 F 2 , through the gas phase at ambient temperatures fol- lowed by desiccation by equilibration with a dry environment. We follow the structure of [(UO 2 ) 7 F 14 (H 2 O) 7 ] 4H 2 O through an intermediate, liquid-like phase, wherein the coordination number of the uranyl ion is reduced to 5 (from 6 in the anhydrous struc- ture), and a water molecule binds as an equatorial ligand to the uranyl ion. Quasielas- tic neutron scattering results compare well with previous measurements of mineral hydrates. The two groups of structurally distinct water molecules in D perform re- stricted motion on a length scale commensurate with the O{H bond (r = 0.92 A). The more tightly bound equatorial ligand waters rotate slower (Dr = 2.2 ps -1 ) than their hydrogen-bonded partners (Dr = 28.7 ps -1 ).

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2019

Optical Stark and Zeeman Spectroscopy of Thorium Fluoride, ThF, and Thorium Chloride, ThCl

Experimentally and theoretically determined magnetic and electric dipole moments, bond distances and vibrational spacings are used for a comparative study of the bonding in ThF and ThCl. Numerous bands in the visible electronic spectra between 16400 cm -1 -18800 cm -1 of supersonically cooled molecular beam samples have been detected using medium resolution (Δν≈ 0.1cm -1 ), two dimensional (2D) spectroscopy. High resolution (Δν < 20 MHz) field-free, Stark, and Zeeman spectroscopy of the detected [18.6] Ω=3/2 – X 2 Δ 3/2 band of ThF near 538.4 nm and the [18.2] Ω=3/2 – X 2 Δ 3/2 band of ThCl near 551.0 nm have been recorded and analyzed. Stark shifts and splitting were analyzed to produce | r μ el | values of 1.453(7) D and 0.588(9) D, for the X 2 Δ 3/2 and [18.6]Ω=3/2 states of ThF, respectively, and 2.022(35) D and 3.020(55) D, for the X 2 Δ 3/2 and [18.2]Ω=3/2 states of ThCl. Zeeman splittings and shifts were analyzed to produce g e values of 1.038(4) and 1.079(4) for the X 2 Δ 3/2 and [18.6]Ω=3/2 states of ThF and 1.130(4) and 1.638(4) for the X 2 Δ 3/2 and [18.2]Ω=3/2 states of ThCl. Analysis of g e values demonstrate that the X 2 Δ 3/2 and [18.6]Ω=3/2 states of ThF and the X 2 Δ 3/2 state of ThCl are predominately 2 Δ 3/2 spin-orbit components, whereas the [18.2] Ω=3/2 state of ThCl is an admixture of 2 Δ 3/2 and 2 Π 3/2 spin-orbit components. A molecular orbital description of the ground states is used to rationalize the observed | r μ el | values for the ThX(X=F,Cl,O and S) series, and garner insight into the bonding mechanism. The dipole moments in the ground state of ThF and ThCl have been calculated using relativistic coupled-cluster methods. It is demonstrated that the systematic inclusion of electron-correlation contributions plays an essential role in obtaining accurate predictions for the dipole-moment values in ThF and ThCl.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗