Trapping and diffusion of fission products in ThO2 and CeO2

Xiao, Haiyan; Zhang, Yongfeng; Weber, William J.

doi:10.1016/j.jnucmat.2011.05.037

Cited by 42 publications

(31 citation statements)

References 42 publications

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“…In the supercell the spin is modified due to the influence of the charge transferred to the halogen so that for I the spin is 1 whereas for Cl it is 0.60. The overall magnetic moment associated with Br at an octahedral interstitial site predicted by Xio et al [20] is 0.88 agreeing well with the current prediction of 0.95. Since the addition of dispersion results in only very small changes to the relaxed structures of ions surrounding the interstitial species, it is not surprising that Fig.…”

Section: Halogen Atoms At Interstitial Sitessupporting

confidence: 88%

“…2b and c shows the Bader charges of the halogen atoms and the net magnetic moments of the supercells around the halogens respectively. The value of the Bader charge (and noting the approximations inherent in the Bader analysis [35,36]) depends on the relative electron affinity of the atom: Cl has the highest electron affinity and has gained 0.48 electrons from the surrounding lattice, Br gains 0.34 electrons (in good agreement with Xio et al [20] who reported a charge transfer to Br of 0.22) while I is predicted to gain no charge.…”

Section: Halogen Atoms At Interstitial Sitessupporting

confidence: 69%

“…2a also shows that dispersion facilitates incorporation because induced polarization is attractive but this is only a small perturbation. Xio et al [20] performed DFT þ U calculations using the local density approximation on fission products including Br at an octahedral interstitial site, neutral vacancy defects and clusters in ThO 2 assuming a reference state of X (i.e. an isolated atom).…”

Section: Halogen Atoms At Interstitial Sitesmentioning

confidence: 99%

“…Thus, we have also calculated the 'relative incorporation energies' for halogens in oxygen vacancy sites (Fig. 3b) as we did in previous work on Xe and Kr incorporation [20] (i.e. relative to the lowest vacancy V O ).…”

Section: Impurity Atoms At Oxygen Vacancy Sitementioning

confidence: 99%

“…Conversely, thoria has been less well studied. Some atomic scale modelling studies on trapping and diffusion of the volatile fission products (Xe, Br, Rb and Cs) [18,20] have been reported but these only considered the incorporation of impurity atoms in neutral point defects and neutral clusters of defects, leaving aside the possibility of incorporation in charged defect configurations. A more extensive study of Xe and Kr has been made [21], which did consider charged as well as neutral defect sites.…”

Section: Introductionmentioning

confidence: 99%

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Energetics of halogen impurities in thorium dioxide

Kuganathan

Ghosh

Arya

et al. 2017

Journal of Nuclear Materials

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a b s t r a c tDefect energies for halogen impurity atoms (Cl, Br and I) in thoria are calculated using the generalized gradient approximation and projector augmented plane wave potentials under the framework of density functional theory. The energy to place a halogen atom at a pre-existing lattice site is the incorporation energy. Seven sites are considered: octahedral interstitial, O vacancy, Th vacancy, Th-O di-vacancy cluster (DV) and the three O-Th-O tri-vacancy cluster (NTV) configurations. For point defects and vacancy clusters, neutral and all possible defect charge states up to full formal charge are considered. The most favourable incorporation site for Cl is the singly charged positive oxygen vacancy while for Br and I it is the NTV1 cluster. By considering the energy to form the defect sites, solution energies are generated. These show that in both ThO 2-x and ThO 2 the most favourable solution equilibrium site for halides is the single positively charged oxygen vacancy (although in ThO 2 , I demonstrates the same solubility in the NTV1 and DV clusters). Solution energies are much lower in ThO 2-x than in ThO 2 indicating that stoichiometry is a significant factor in determining solubility. In ThO 2 , all three halogens are highly insoluble and in ThO 2-x Br and I remain insoluble. Although ½Cl 2 is soluble in ThO 2-x alternative phases such as ZrCl 4 exist which are of lower energy.

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Section: Halogen Atoms At Interstitial Sitessupporting

confidence: 88%

Section: Halogen Atoms At Interstitial Sitessupporting

confidence: 69%

Section: Halogen Atoms At Interstitial Sitesmentioning

confidence: 99%

Section: Impurity Atoms At Oxygen Vacancy Sitementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Energetics of halogen impurities in thorium dioxide

Kuganathan

Ghosh

Arya

et al. 2017

Journal of Nuclear Materials

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The Sluggish Diffusion of Cations in CeO₂ Probed through Molecular Dynamics and Metadynamics Simulations

et al. 2023

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Cation diffusion in fluorite‐structured CeO2, though far slower than anion diffusion, is an important, high‐temperature process because it governs diverse fabrication and degradation phenomena. Herein, cation diffusion is studied by means of classical molecular dynamics and metadynamics simulations. Three different mechanisms are examined: migration involving an isolated cerium vacancy, migration involving a cerium vacancy in a defect associate with an oxygen vacancy, and migration involving a cation divacancy. For each mechanism, defect diffusion coefficients are calculated as a function of temperature, from which the respective activation enthalpy of defect migration is obtained. Through comparisons with experimental cation diffusion data (specifically, of the absolute magnitude of the cation diffusivity as well as its activation enthalpy), it is concluded that cation diffusion takes place predominantly neither by isolated vacancies nor by cation vacancy–oxygen vacancy associates but by cation divacancies.

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