Skip to Main content Skip to Navigation
Journal articles

Lattice constant in nonstoichiometric uranium dioxide from first principles

Abstract : Nonstoichiometric uranium dioxide experiences a shrinkage of its lattice constant with increasing oxygen content, in both the hypostoichiometric and the hyperstoichiometric regimes. Based on first-principles calculations within the density functional theory (DFT)+$U$ approximation, we have developed a point defect model that accounts for the volume of relaxation of the most significant intrinsic defects of UO$_2$. Our point defect model takes special care of the treatment of the charged defects in the equilibration of the model and in the determination of reliable defect volumes of formation. In the hypostoichiometric regime, the oxygen vacancies are dominant and explain the lattice constant variation with their surprisingly positive volume of relaxation. In the hyperstoichiometric regime, the uranium vacancies are predicted to be the dominating defect,in contradiction with experimental observations. However, disregarding uranium vacancies allows us to recover a good match for the lattice-constant variation as a function of stoichiometry. This can be considered a clue that the uranium vacancies are indeed absent in UO$_{2+x}$ , possibly due to the very slow diffusion of uranium.
Complete list of metadatas

Cited literature [60 references]  Display  Hide  Download

https://hal-cea.archives-ouvertes.fr/cea-02063621
Contributor : Michel Freyss <>
Submitted on : Monday, March 11, 2019 - 12:55:09 PM
Last modification on : Friday, July 31, 2020 - 9:24:08 AM
Long-term archiving on: : Wednesday, June 12, 2019 - 2:33:21 PM

File

2018_Bruneval_PRMat2.pdf
Publisher files allowed on an open archive

Identifiers

Citation

Fabien Bruneval, Michel Freyss, Jean-Paul Crocombette. Lattice constant in nonstoichiometric uranium dioxide from first principles. Physical Review Materials, American Physical Society, 2018, 2, pp.023801. ⟨10.1103/PhysRevMaterials.2.023801⟩. ⟨cea-02063621⟩

Share

Metrics

Record views

106

Files downloads

255