Computational study of the energetics of charge and cation mixing in U<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:math>Ce<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mi>x</mml:mi></mml:msub></mml:math>O<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>2</mm

Hanken, Benjamin E.; Stanek, Christopher R.; Grønbech‐Jensen, Niels; Asta, Mark

doi:10.1103/physrevb.84.085131

Cited by 37 publications

(27 citation statements)

References 41 publications

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“…7,8,9 The number of vacancies required for xenon diffusion or the mechanism by which the xenonvacancy complex diffuse is not known experimentally. Because of the difficulty of measuring atomic scale properties, calculating these properties in UO 2 has been of interest using both Density Functional Theory (DFT) 7,10,11,12,13,14,15,16,17,18,19 as well as empirical potentials. 8,9,11,12,19,20,21,22,23 Several theoretical investigations of xenon in UO 2 have studied diffusion via a tetravacancy (TV, 2 V U + 2 V O ) mechanism.…”

Section: Introductionmentioning

confidence: 99%

Pathway and energetics of xenon migration in uranium dioxide

Thompson

Wolverton

2013

Phys. Rev. B

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Using a combination of Density Functional Theory (DFT), classical potentials, Molecular Dynamics (MD), and Nudged Elastic Band (NEB) calculations, we explore the diffusion of xenon in uranium dioxide (UO 2 ). We compare migration barriers of empirical potentials with DFT by performing NEB calculations and subsequently we use the DFT-validated empirical potentials to calculate vacancy clusters, with and without xenon, to determine the migration path and barrier of xenon in bulk UO 2 . We find (i) two empirical potentials out of four tested agree qualitatively with DFT derived energetics for Schottky defect migration, (ii) through the use of molecular dynamics with empirical potentials, we have found a new path for the diffusion of xenon-tetravacancy clusters (Xe + 2 V U + 2 V O ), (iii) this new path has an energy barrier significantly lower than previously reported paths by nearly 1 eV, (iv) we examine the physical contributions to the migration pathway and find the barrier is largely electrostatic and that xenon contributes very little to the barrier height, (v) once a uranium vacancy attaches to a xenonSchottky defect, the resulting xenon-tetravacancy cluster is strongly bound, and (vi) like xenon in a tetravacancy, a xenon-double Schottky defect can diffuse in a concerted manor with a comparable barrier to xenon in a tetravacancy, but two of the oxygen vacancies are only weakly bound to the defect.

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Section: Introductionmentioning

confidence: 99%

Pathway and energetics of xenon migration in uranium dioxide

Thompson

Wolverton

2013

Phys. Rev. B

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“…It is also important to note that Hanken et al [15] ordering models equivalent to our pure layer models (namely their "CdI 2 " and "CuPt"…”

Section: Resultsmentioning

confidence: 84%

“…In any case, there are numerous theoretical studies of uranium-bearing complex oxides published in the literature, such as calculations of the electronic structure of Uranium-Americium complex oxides using DFT by Suzuki et al [14]. Another important study related to the work presented here involves molecular dynamics and DFT simulations of solid solutions of Ce 2 O 3 -UO 2 -UO 3 by Hanken et al [15,16], to establish the energetics of cation mixing.…”

Section: Introductionmentioning

confidence: 99%

Structure and cation ordering in La2UO6, Ce2UO6, LaUO4, and CeUO4 by first principles calculations

Casillas-Trujillo

McMurray

et al. 2016

Computational Materials Science

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International audienceIn the present work, we have used density functional theory (DFT) and DFT+U to investigate the crystal structure and phase stability of four model compounds in the Ln 2 O 3-UO 2-UO 3 ternary oxide system: La 2 UO 6 , Ce 2 UO 6 , LaUO 4 , CeUO 4 , due to the highly-correlated nature of the f-electrons in uranium. We have considered both hypothetical ordered compounds and compounds in which the cations randomly occupy atomic sites in a fluorite-like lattice. We determined that ordered compounds are stable and are energetically favored compared to disordered configurations, though the ordering tendencies are weak. To model and analyze the structures of these complex oxides, we have used supercells based on a layered atomic model. In the layer model, the supercell is composed of alternating planes of anions and cations. We have considered two different ordering motifs for the cations, namely single species (isoatomic) cation layers versus mixed species cation layers. Energy differences between various ordered cationic arrangements were found to be small. This may have implications regarding radiation stability, since cationic arrangements should be able to change under irradiation with little cost in energy

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“…In these calculations, a Hubbard-U correction was implemented within the formalism of Dudarev et al [39] to account for the self-interaction error for localized 5f electrons in uranium. The value of the parameter U eff = U-J in the DFT + U formalism was chosen to be 4.00 eV for this study; this value is similar to that found to give optimal results in comparisons with spectroscopic data for UO 2 by Dudarev et al (3.99 eV) [39], and was found to provide good agreement between calculated and measured oxidation enthalpies of UO 2 [40]. The PAW potentials used in this work are U, O, Y_sv and La in the VASP PBE library.…”

Section: First-principles Calculationsmentioning

confidence: 87%

Computational study of the energetics and defect clustering tendencies for Y- and La-doped UO2

et al. 2014

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The energetics and defect ordering tendencies in solid solutions of fluorite-structured UO 2 with trivalent rare earth cations (M 3+ = Y, La) are investigated computationally using a combination of ionic pair potential and density functional theory based methods. Calculated enthalpies of formation with respect to constituent oxides show higher energetic stability for La solid solutions than for Y. Additionally, calculations performed for different atomic configurations show a preference for reduced (increased) oxygen vacancy coordination around La (Y) dopants. The current results are shown to be qualitatively consistent with related calculations and calorimetric measurements of heats of formation in other trivalent doped fluorite oxides, which show a tendency for increasing stability and increasing preference for higher oxygen coordination with increasing size of the trivalent impurity. The implications of these results are discussed in the context of the effect of trivalent impurities on oxygen ion mobilities in UO 2 , which are relevant to the understanding of experimental observations concerning the effect of trivalent fission products on the oxidative corrosion rates of spent nuclear fuel.

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Computational study of the energetics of charge and cation mixing in U1−xCexO2

Cited by 37 publications

References 41 publications

Pathway and energetics of xenon migration in uranium dioxide

Pathway and energetics of xenon migration in uranium dioxide

Structure and cation ordering in La2UO6, Ce2UO6, LaUO4, and CeUO4 by first principles calculations

Computational study of the energetics and defect clustering tendencies for Y- and La-doped UO2

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