Pressure-induced evolution of the lattice dynamics for selected UO3 polymorphs
•Four phases of UO3 investigated up to 45 GPa with density functional theory.•Two phases exhibit isotropic response to pressure; two an anisotropic response.•Eigenvector decomposition tracks changes in coordination environment via phonon modes. Uranium trioxide (UO3) is a stable chemical form of ura...
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Veröffentlicht in: | Journal of nuclear materials 2023-10, Vol.584, p.154577, Article 154577 |
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Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | •Four phases of UO3 investigated up to 45 GPa with density functional theory.•Two phases exhibit isotropic response to pressure; two an anisotropic response.•Eigenvector decomposition tracks changes in coordination environment via phonon modes.
Uranium trioxide (UO3) is a stable chemical form of uranium oxide with multiple polymorphs found throughout the nuclear fuel cycle. The pressure-induced changes in the structure and lattice dynamics of four of these polymorphs are simulated with density functional perturbation theory and analyzed. Two phases, α- and δ-UO3 are found to exhibit an isotropic response to pressure and do not undergo any changes in coordination geometry up to ∼40 GPa. In contrast, the other two phases investigated, β- and γ-UO3, exhibit an anisotropic response to pressure. Decomposition of the phonon eigenvectors allows us to assign specific pressure-induced structural changes to individual phonon modes. This analysis has been performed on a per atom basis for the relatively simple α- and δ-UO3 structures, which have one symmetrically unique uranium site, and on a per coordination environment basis for β- and γ-UO3, which have multiple U sites. |
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ISSN: | 0022-3115 1873-4820 |
DOI: | 10.1016/j.jnucmat.2023.154577 |