Structural Phase Transitions and Water Dynamics in Uranyl Fluoride Hydrates

Andrew Miskowiec, Marie C. Kirkegaard, Ashfia Huq, Eugene Mamontov, Kenneth W. Herwig, Lee Trowbridge, Adam Rondinone, Brian Anderson

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12 Scopus citations

Abstract

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).

Original languageEnglish
Pages (from-to)11900-11910
Number of pages11
JournalJournal of Physical Chemistry A
Volume119
Issue number49
DOIs
StatePublished - Dec 10 2015

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