In this work, the incorporation, diffusion, and clustering behaviors of He atoms in uranium mononitride (UN) and the effects of Zr atoms on these behaviors have been investigated based on density-functional theory. It is found that interstitial site is the most favorable site for He atom. U vacancy acts as the trapping center for He atoms, and it can trap eight He atoms. While with Zr, the U vacancy can trap more He atoms (at least nine), which indicates that Zr atoms can help U vacancies to accommodate more He atoms. In addition, the presence of Zr atoms could change the optimal diffusion path of the interstitial He atom to the U vacancy site, verified by the calculated diffusion barrier energy. The present results are expected to provide fundamental information to the evolution mechanism of He bubbles in UN fuels.

Graphical abstract

中文翻译：

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Zr 对 He 在一氮化铀中的掺入、扩散和聚集行为的影响：第一性原理研究

在这项工作中，基于密度泛函理论研究了He原子在一氮化铀（UN）中的掺入、扩散和聚集行为以及Zr原子对这些行为的影响。研究发现，间隙位点是He原子最有利的位点。U空位作为He原子的俘获中心，可以俘获8个He原子。而对于Zr，U空位可以捕获更多的He原子（至少9个），这表明Zr原子可以帮助U空位容纳更多的He原子。此外，Zr原子的存在可以改变间隙He原子到U空位位点的最佳扩散路径，这通过计算的扩散势垒能得到验证。目前的结果有望为联合国燃料中氦气泡的演化机制提供基本信息。

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