Vacancy-enhanced mechanism for helium diffusion along Σ7 grain boundary in α-Al₂O₃: A first principle study

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• 作者：Fei Wang^a ; ^b ; Wensheng Lai^a ; ^{wslai@tsinghua.edu.cn} ; Rusong Li^b ; Bin He^b ; Sufen Li^b
• 关键词：First-principles calculations ; Grain boundary ; Helium ; Diffusion ; Alpha-Al2O3
• 刊名：Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
• 出版年：2017
• 出版时间：15 February 2017
• 年：2017
• 卷：393
• 期：Complete
• 页码：88-92
• 全文大小：1177 K
• 卷排序：393

文摘

Helium migration behavior in the bulk and along the rhombohedral Σ7 grain boundary (GB) of α-Al2O3 has been studied via first-principles calculations based on the projector-augmented wave method. It turns out that the formation energies of helium in the α-Al2O3 bulk and in the rhombohedral Σ7 GB area are 2.12 eV and 3.15 eV, respectively. The energy barrier for helium migration in bulk is 2.28 eV, indicating that helium is difficult to diffuse. Moreover, the calculations also reveal that the radiation-induced O vacancies are favored to aggregate to the Σ7 GB plane, forming a zigzag O vacancy chain. In such circumvent, however, the energy barrier for helium diffusion along vacancy chain is significantly reduced to 0.61 eV, suggesting such O vacancy chain would provide the fast diffusion path for helium to escape from α-Al2O3 due to its large positive formation energy in the bulk.