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Title: Computational study of the energetics of charge and cation mixing in U1-xCexO₂

The formalism of electronic density-functional theory (DFT), with Hubbard-U corrections (DFT+U), is employed in a computational study of the energetics of fluorite-structured U1-xCexO₂ mixtures. The computational approach makes use of a procedure which facilitates convergence of the calculations to multiple self-consistent DFT+U solutions for a given cation arrangement, corresponding to different charge states for the U and Ce ions in several prototypical cation arrangements. Results indicate a significant dependence of the structural and energetic properties on the nature of both charge and cation ordering. With the effective Hubbard-U parameters that reproduce well the measured oxidation-reduction energies for urania and ceria, we find that charge transfer between U⁴⁺ and Ce⁴⁺ ions, leading to the formation of U⁵⁺ and Ce³⁺, gives rise to an increase in the mixing energy in the range of 4–14 kJ/mol of the formula unit, depending on the nature of the cation ordering. The results suggest that although charge transfer between uranium and cerium ions is disfavored energetically, it is likely to be entropically stabilized at the high temperatures relevant to the processing and service of urania-based solid solutions.
Authors:
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Publication Date:
OSTI Identifier:
1100644
Type:
Publisher's Accepted Manuscript
Journal Name:
Physical Review. B, Condensed Matter and Materials Physics
Additional Journal Information:
Journal Volume: 84; Journal Issue: 8; Journal ID: ISSN 1098-0121
Publisher:
American Physical Society
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English