Investigation on mechanical behavior of single-layer graphene with grain boundary loops

Graphene is one of the most promising materials in nanotech nology. It is crucial to establish reliable structure-property relationships in the important two-dimensional crystals- graphene-to fully use their remarkable properties. With the success in synthesizing large-area polycrystalline graphene, understanding how grain boundary loops in graphene alter its physical properties is of both scientific and technological importance. We show in the chapter that grain boundary loops can either increase or decrease breaking strength of graphene along the armchair or zigzag direction, and the behavior can be explained well by continuum mechanics. It is not just the density of defects that affects the mechanical properties, but the geometrical arrangements and space relative position of disclination dipoles also play an important role. A novel rule can be used to predict the breaking strength of graphene accu rately, whose restriction lies in that only one heptagon is the nearest to each pentagon, such as the C₃, C₆(2,1), and C₆(3,1) grain boundary loop, and the trend breaks down in other cases. It proves that the topological nature of a certain type of grain boundary loop in polycrystalline graphene may be used to design physical properties on a nanoscale.