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Interplay of defect cluster and the stability of xenon in uranium dioxide from density functional calculations

机译：从密度泛函计算中缺陷簇的相互作用和氙在二氧化铀中的稳定性

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摘要

Self-defect clusters in bulk matrix might affect the thermodynamic behavior of fission gases in nuclear fuel such as uranium dioxide. With first-principles local spin-density approximation plus U calculations and taking xenon as a prototype, we find that the influence of oxygen defect clusters on the thermodynamics of gas atoms is prominent, which increases the solution energy of xenon by a magnitude of 0.5 eV, about 43% of the energy difference between the two lowest lying states at 700 K. Calculation also reveals a thermodynamic competition between the uranium vacancy and trivacancy sites to incorporate xenon in hyperstoichiometric regime at high temperatures. The results show that in hypostoichiometric regime neutral trivacancy sites are the most favored position for diluted xenon gas, whereas in hyperstoichiometric condition they prefer to uranium vacancies even after taking oxygen self-defect clusters into account at low temperatures, which not only confirms previous studies but also extends the conclusion to more realistic fuel operating conditions. The observation that gas atoms are ionized to a charge state of Xe~+ when at a uranium vacancy site due to strong Madelung potential implies that one can control temperature to tune the preferred site of gas atoms and then the bubble growth rate. A solution to the notorious metastable states difficulty that frequently encountered in density functional theory plus U applications, namely, the quasiannealing procedure, is also discussed.
机译：本体基质中的自缺陷簇可能会影响核燃料（如二氧化铀）中裂变气体的热力学行为。通过第一原理的局部自旋密度逼近加U计算并以氙气为原型，我们发现氧缺陷簇对气体原子热力学的影响非常显着，从而使氙的溶液能提高了0.5 eV。在700 K时，两个最低躺着状态之间的能量差约为43％。计算还揭示了在高温下，铀的空位和三空位之间会发生热力学竞争，从而在高化学计量状态下掺入氙。结果表明，在化学计量不足的条件下，中性三空位是稀释氙气的最有利位置，而在化学计量过量的条件下，即使考虑了低温下的氧自缺陷簇，它们也倾向于铀空位，这不仅证实了先前的研究，而且还将结论扩展到更现实的燃料运行条件。由于强大的马德隆势能，在铀空位处，气体原子被离子化为Xe〜+的电荷状态，这表明人们可以控制温度以调节气体原子的优选位置，然后调节气泡的生长速率。还讨论了解决臭名昭著的亚稳态问题的方法，该方法在密度泛函理论和U应用程序中经常遇到，即拟退火程序。

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  • 来源
    《Physical review》 |2010年第9期|p.094106.1-094106.9|共9页
  • 作者

    Hua Y. Geng; rnYing Chen; rnYasunori Kaneta; rnMotoyasu Kinoshita; rnQ. Wu;

  • 作者单位

    National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, CAEP,P.O. Box 919-102, Mianyang, Sichuan 621900, People's Republic of China;

    rnDepartment of Systems Innovation, The University of Tokyo, Hongo 7-3-1, Tokyo 113-8656, Japan;

    Department of Systems Innovation, The University of Tokyo, Hongo 7-3-1, Tokyo 113-8656, Japan;

    Nuclear Technology Research Laboratory, Central Research Institute of Electric Power Industry, Tokyo 201-8511, Japan Japan Atomic Energy Agency, Ibaraki 319-1195, Japan;

    rnNational Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, CAEP,P.O. Box 919-102, Mianyang, Sichuan 621900, People's Republic of China;

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  • 正文语种 eng
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  • 关键词

    total energy and cohesive energy calculations; strongly correlated electron systems; heavy fermions;

    机译：总能量和内聚能计算;强相关电子系统;重费米子;

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