Structural Phase Transitions and Water Dynamics in Uranyl Fluoride Hydrates

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• 作者：Andrew Miskowiec ; Marie C. Kirkegaard ; Ashfia Huq ; Eugene Mamontov ; Kenneth W. Herwig ; Lee Trowbridge ; Adam Rondinone ; Brian Anderson
• 刊名：Journal of Physical Chemistry A
• 出版年：2015
• 出版时间：December 10, 2015
• 年：2015
• 卷：119
• 期：49
• 页码：11900-11910
• 全文大小：588K
• ISSN：1520-5215

文摘

We report a novel production method for uranium oxyfluoride [(UO₂)₇F₁₄(H₂O)₇]路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]路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鈥揌 bond (r = 0.92 脜). The more tightly bound equatorial ligand waters rotate slower (D_r = 2.2 ps^鈥?) than their hydrogen-bonded partners (D_r = 28.7 ps^鈥?).