Interactions between vacancies and prismatic Σ3 grain boundary in α-Al₂O₃: First principles study

Interactions between vacancies and Σ3 prismatic screw-rotation grain boundary in α-Al₂O₃ are investigated by the first principles projector-augmented wave method. It turns out that the vacancy formation energy decreases with reducing the distance between vacancy and grain boundary (GB) plane and reaches the minimum on the GB plane (at the atomic layer next to the GB) for an O (Al) vacancy. The O vacancy located on the GB plane can attract other vacancies nearby to form an O-O di-vacancy while the Al vacancy cannot. Moreover, the O-O di-vacancy can further attract other O vacancies to form a zigzag O vacancy chain on the GB plane, which may have an influence on the diffusion behavior of small atoms such as H and He along the GB plane of α-Al₂O₃.