Refractory molybdenum-rhenium (Mo-) alloys are considered as the best core structural materials in the space nuclear reactor. Irradiation will induce obvious microstructure damage and formation of -rich precipitates, but the underlying mechanism remains unclear due to the complicated interaction between and defects. In this work, by using first-principles and molecular static calculations, we obtain the thermodynamically stable configurations and binding energies of vacancy and vacancy- clusters in bulk Mo. A general expression of the vacancy binding energy for a stable vacancy cluster is proposed, which is determined by the numbers of the formed 1st and 2nd nearest neighboring vacancy-vacancy pairs. A scenario for the clustering of vacancy and is also revealed. With the presence of solute in Mo, the vacancy clustering initiates when the vacancy number reaches a certain value. Prior to the vacancy aggregation, the newly-added vacancy combines with the present and other vacancies, due to the strong attraction of -vacancy. It is noteworthy that the formed vacancy- and vacancy--vacancy pairs contribute to the vacancy binding energies in Mo- system. Especially for the formed V-Re complex, it could not only indicate the initiation of vacancy clustering, but also be the nucleus for further segregation towards the vacancy cluster. Our results provide fundamental insight to the irradiation-induced formation of -rich clusters in Mo- system, from the aspect of the atomic interaction between and vacancy.

中文翻译：

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配位环境主导钼中空位和铼的团聚行为


难熔钼铼（Mo-）合金被认为是空间核反应堆最好的堆芯结构材料。辐照会引起明显的微观结构损伤并形成富沉淀物，但由于缺陷之间复杂的相互作用，其潜在机制仍不清楚。在这项工作中，通过使用第一性原理和分子静态计算，我们获得了块体Mo中空位和空位簇的热力学稳定构型和结合能。提出了稳定空位簇的空位结合能的通用表达式，由形成的第一和第二最近相邻空位-空位对的数量确定。还揭示了空缺聚集的场景。由于Mo中存在溶质，当空位数达到一定值时，空位聚集开始。在空缺聚集之前，由于-空缺的强大吸引力，新增空缺与现有空缺和其他空缺合并。值得注意的是，形成的空位-和空位-空位对有助于Mo-系统中的空位结合能。特别是对于形成的V-Re配合物，它不仅可以指示空位团簇的开始，而且可以成为空位团团进一步偏析的核。我们的研究结果从原子与空位之间相互作用的角度，为 Mo- 系统中辐照诱导富集簇的形成提供了基本的见解。