Abstract
Refractory molybdenum-rhenium (Mo-Re) alloys are considered as the best core structural materials in the space nuclear reactor. Irradiation will induce obvious microstructure damage and formation of Re-rich precipitates, but the underlying mechanism remains unclear due to the complicated interaction between Re 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-Re 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 Re is also revealed. With the presence of solute Re 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 Re and other vacancies, due to the strong attraction of Re-vacancy. It is noteworthy that the formed vacancy-Re and vacancy-Re-vacancy pairs contribute to the vacancy binding energies in Mo-Re system. Especially for the formed V2-Re1 complex, it could not only indicate the initiation of vacancy clustering, but also be the nucleus for further Re segregation towards the vacancy cluster. Our results provide fundamental insight to the irradiation-induced formation of Re-rich clusters in Mo-Re system, from the aspect of the atomic interaction between Re and vacancy.
Published Version
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