First-principles investigation of the bulk properties of americium dioxide and sesquioxides

Noutack, Martin S. Talla; Geneste, Grégory; Jomard, Gérald; Freyss, Michel

doi:10.1103/physrevmaterials.3.035001

Cited by 15 publications

(17 citation statements)

References 49 publications

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“…We obtain a static dielectric constant of 19.66. This compares favourably to the experimental value (18.9 59 ) and falls between the experimental value for UO 2 (23.8 60 ) and the DFTobtained value for AmO 2 (17.40 61 ), thus fits within the emerging trend.…”

Section: Finite Size Correctionsupporting

confidence: 87%

The defect chemistry of non-stoichiometric PuO_2±x

Neilson

Pegg

Steele

et al. 2021

Phys. Chem. Chem. Phys.

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Section: Finite Size Correctionsupporting

confidence: 87%

The defect chemistry of non-stoichiometric PuO_2±x

Neilson

Pegg

Steele

et al. 2021

Phys. Chem. Chem. Phys.

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“…The PBEsol + U functional is used with U set to 4 eV, SOI considered, and a 5 × 5 × 5 k -point mesh applied. For AmO 2 , transverse 3k AFM order is applied, while we simulate A-type Am 2 O 3 with longitudinal 1k AFM order . The bulk properties produced with these simulation parameters are reasonable compared to experiment (see the Supporting Information).…”

Section: Methodsmentioning

confidence: 68%

Evolving Defect Chemistry of (Pu,Am)O_2±x

2021

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The β decay of 241 Pu to 241 Am results in a significant ingrowth of Am during the interim storage of PuO 2 . Consequently, the safe storage of the large stockpiles of separated Pu requires an understanding of how this ingrowth affects the chemistry of PuO 2 . This work combines density functional theory (DFT) defect energies and empirical potential calculations of vibrational entropies to create a point defect model to predict how the defect chemistry of PuO 2 evolves due to the incorporation of Am. The model predicts that Am occupies Pu sites in (Pu,Am)O 2± x in either the +III or +IV oxidation state. High temperatures, low oxygen-to-metal (O/M) ratios, or low Am concentrations favor Am in the +III oxidation state. Am (+III) exists in (Pu,Am)O 2± x as the negatively charged (Am Pu 1– ) defect, requiring charge compensation from holes in the valence band, thereby increasing the conductivity of the material compared to Am-free PuO 2 . Oxygen vacancies take over as the charge compensation mechanism at low O/M ratios. In (Pu,Am)O 2± x , hypo- and (negligible) hyperstoichiometry is found to be provided by the doubly charged oxygen vacancy (V O 2+ ) and singly charged oxygen interstitial (O i 1– ), respectively.

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“…The focus of metastable states in actinide materials has largely been limited to UN ,, and uranium oxides. ,− ,− For UO 2 and a U value of 4.5 eV, we identify nine metastable states with energies of 0.01–0.90 eV (per formula unit) above the ground state. This is in good quantitative agreement with the previous work of Dorado et al, who identified eight metastable states spanning an energy range of 0.02–0.86 eV above the ground state for the same U value.…”

Section: Resultsmentioning

confidence: 99%

“…The PAW data sets used in this paper were taken from PSLibrary version 1.00 . While a new set of pseudopotentials have recently been developed specifically for UC, UN, and UO 2 , we continue to use the standard pseudopotentials to maintain consistency with previous computational studies. ,− ,− For structural relaxation, a 6 × 6 × 6 k -point mesh was used for UC, UN, and UO 2 , while a 4 × 4 × 4 mesh was used for UCl 3 . These meshes were found to yield converged calculated structures.…”

Section: Methodsmentioning

confidence: 99%

Interplay between London Dispersion, Hubbard U, and Metastable States for Uranium Compounds

2021

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High-throughput computational studies of lanthanide and actinide chemistry with density-functional theory are complicated by the need for Hubbard U corrections, which ensure localization of the f-electrons, but can lead to metastable states. This work presents a systematic investigation of the effects of both Hubbard U value and metastable states on the predicted structural and thermodynamic properties of four uranium compounds central to the field of nuclear fuels: UC, UN, UO2, and UCl3. We also assess the impact of the exchange-hole dipole moment (XDM) dispersion correction on the computed properties. Overall, the choice of Hubbard U value and inclusion of a dispersion correction cause larger variations in the computed geometric properties than result from metastable states. The weak dependence of structure optimization on metastable states should simplify future high-throughput calculations on actinides. Conversely, addition of the dispersion correction is found to offset the repulsion introduced by the Hubbard U term and provides greatly improved agreement with experiment for both cell volumes and heats of formation. The XDM dispersion correction is largely invariant to the chosen U value, making it a robust dispersion correction for actinide systems.

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First-principles investigation of the bulk properties of americium dioxide and sesquioxides

Cited by 15 publications

References 49 publications

The defect chemistry of non-stoichiometric PuO_2±x

The defect chemistry of non-stoichiometric PuO_2±x

Evolving Defect Chemistry of (Pu,Am)O_2±x

Interplay between London Dispersion, Hubbard U, and Metastable States for Uranium Compounds

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First-principles investigation of the bulk properties of americium dioxide and sesquioxides

Cited by 15 publications

References 49 publications

The defect chemistry of non-stoichiometric PuO2±x

The defect chemistry of non-stoichiometric PuO2±x

Evolving Defect Chemistry of (Pu,Am)O2±x

Interplay between London Dispersion, Hubbard U, and Metastable States for Uranium Compounds

Contact Info

Product

Resources

About

The defect chemistry of non-stoichiometric PuO_2±x

The defect chemistry of non-stoichiometric PuO_2±x

Evolving Defect Chemistry of (Pu,Am)O_2±x