Energetics and defect clustering trends for trivalent rare earth cations substituted in UO2

Solomon, Jonathon; Navrotsky, A.; Asta, Mark

doi:10.1016/j.jnucmat.2014.11.089

Cited by 9 publications

(7 citation statements)

References 39 publications

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“…The eigen states are expanded by using plane wave basis function within the framework of projector augmented wave (PAW) method . The PAW method is used to calculate the structural properties of C‐type lanthanide sesquioxides in the previously reported theoretical calculations and is in good agreement with available experimental results . The PAW potentials used in the present work are O, Pm_3, Sm_3, Eu_3, Gd_3, Tb_3, and Dy_3 from the VASP database.…”

Section: Methodsmentioning

confidence: 63%

“…Since the results are almost same, 4 × 4 × 4 k‐point grid is used for all our calculations. In the literature, k‐point grid of 4 × 4 × 4 or even smaller grid point are used for the C‐type lanthanide sesquioxides and excellent results are obtained. The crystal structure for all Ln 2 O 3 lattices is fully relaxed allowing both atoms and lattice constants to change.…”

Section: Resultsmentioning

confidence: 99%

“…Here, the “_3” in the PAW potential denotes that the f ‐electrons in 4f orbitals of lanthanide ions in its trivalent oxidation state are partly treated as core electrons matching the formal valency 3. These potentials produced excellent results for rare earth oxides . An energy cutoff value of 500 eV is used for the plane wave expansion.…”

Section: Methodsmentioning

confidence: 99%

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Ab Initio Study on Structure, Elastic, and Mechanical Properties of Lanthanide Sesquioxides

Pathak

Vazhappilly

2018

Physica Status Solidi (b)

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The structural, mechanical and elastic properties of industrially important Ctype lanthanide sesquioxides, Ln 2 O 3 (Ln ¼ Pm, Sm, Eu, Gd, Tb, Dy), are studied by employing ab initio electronic structure calculations. The calculated lattice parameters for Ln 2 O 3 match very well with the experimental crystal structures and clearly reproduce the lanthanide contraction across the lanthanide series. Similarly, the elastic constants, bulk modulus and other mechanical properties obtained from our calculations are in very good agreement with the values available in the literature. The knowledge about bulk modulus and shear modulus could provide the volume and shape variation of material with respect to external strain which has significant impact for selecting suitable materials for novel applications.

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Section: Methodsmentioning

confidence: 63%

Section: Resultsmentioning

confidence: 99%

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Ab Initio Study on Structure, Elastic, and Mechanical Properties of Lanthanide Sesquioxides

Pathak

Vazhappilly

2018

Physica Status Solidi (b)

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“…In the latter case, although configurational long-range order is absent on the cation and anion sublattices, experimental studies based on advanced structural characterization and thermochemistry techniques (e.g., refs 4, 5, 6, 7, 8 and references therein) have documented in several systems the presence of significant short-range order, i.e., local association and clustering of the different ionic species and oxygen vacancies. These experimental studies have been augmented by atomic-scale computational investigations (e.g., refs 9, 10, 11, 12, 13, 14, 15, 16 and references therein), which have established preferred structural motifs and associated energetic driving forces for defect association and compositional ordering across a broad range of chemistries.…”

mentioning

confidence: 99%

Chemical ordering in substituted fluorite oxides: a computational investigation of Ho2Zr2O7 and RE2Th2O7 (RE=Ho, Y, Gd, Nd, La)

Solomon

Shamblin

Lang

et al. 2016

Sci Rep

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Fluorite-structured oxides find widespread use for applications spanning nuclear energy and waste containment, energy conversion, and sensing. In such applications the host tetravalent cation is often partially substituted by trivalent cations, with an associated formation of charge-compensating oxygen vacancies. The stability and properties of such materials are known to be influenced strongly by chemical ordering of the cations and vacancies, and the nature of such ordering and associated energetics are thus of considerable interest. Here we employ density-functional theory (DFT) calculations to study the structure and energetics of cation and oxygen-vacancy ordering in Ho2Zr2O7. In a recent neutron total scattering study, solid solutions in this system were reported to feature local chemical ordering based on the fluorite-derivative weberite structure. The calculations show a preferred chemical ordering qualitatively consistent with these findings, and yield values for the ordering energy of 9.5 kJ/mol-cation. Similar DFT calculations are applied to additional RE2Th2O7 fluorite compounds, spanning a range of values for the ratio of the tetravalent and trivalent (RE) cation radii. The results demonstrate that weberite-type order becomes destabilized with increasing values of this size ratio, consistent with an increasing energetic preference for the tetravalent cations to have higher oxygen coordination.

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“…Computational investigations of the energetics of rare earth substituted urania solid solutions have also been reported only relative recently [20]. In contrast to the experimental investigations, which focused on stoichiometric and hyperstoichiometric oxygen to metal ratios, the computational work published to date investigated hypostoichiometric compositions where charge compensation occurs through oxygen vacancies.…”

Section: Introductionmentioning

confidence: 99%

A combined calorimetric and computational study of the energetics of rare earth substituted UO2 systems

et al. 2015

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The energetics of rare earth substituted UO 2 solid solutions (U 1-x Ln x O 2-0.5x+y , where Ln = La, Y, and Nd) are investigated employing a combination of calorimetric measurements and density functional theory based computations. Calculated and measured formation enthalpies agree within 10 kJ/mol for stoichiometric oxygen/metal compositions. To better understand the factors governing the stability and defect binding in rare earth substituted urania solid solutions, systematic trends in the energetics are investigated based on the present results and previous computational and experimental thermochemical studies of rare earth substituted fluorite oxides (A 1-x Ln x O 2-0.5x , where A = Hf, Zr, Ce, and Th). A consistent trend towards increased energetic stability with larger size mismatch between the smaller host tetravalent cation and the larger rare earth trivalent cation is found for both actinide and non-actinide fluorite oxide systems where aliovalent substitution of Ln cations is compensated by oxygen vacancies. However, the large exothermic oxidation enthalpy in the UO 2 based systems favors oxygen rich compositions where charge compensation occurs through the formation of uranium cations with higher oxidation states.

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Energetics and defect clustering trends for trivalent rare earth cations substituted in UO2

Cited by 9 publications

References 39 publications

Ab Initio Study on Structure, Elastic, and Mechanical Properties of Lanthanide Sesquioxides

Ab Initio Study on Structure, Elastic, and Mechanical Properties of Lanthanide Sesquioxides

Chemical ordering in substituted fluorite oxides: a computational investigation of Ho2Zr2O7 and RE2Th2O7 (RE=Ho, Y, Gd, Nd, La)

A combined calorimetric and computational study of the energetics of rare earth substituted UO2 systems

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