Single vacancy defects diffusion at the initial stage of graphene growth: A first-principles study

•The migration of single vacancy in graphene fragment.•The interaction between single vacancy and five- or seven-membered ring.•The possible reason why it is difficult to find single vacancy inside graphene.

The migration of a single vacancy (SV) defect in graphene fragment (GF) has been investigated by density functional theory (DFT). The results revealed that a single vacancy defect is easy to migrate to the GF edge. The interaction between an SV and a five-numbered ring at the edge results in two neighboring five-membered rings finally, while the interaction between an SV and a seven-membered ring defect at the edge of the GF leads to a five-numbered ring and a neighbor seven-numbered ring. Our findings shed light upon understanding of the growth process of the graphene grain boundary.