▎ 摘　　要

We conducted molecular dynamics simulations to investigate the atomistic edge crack-vacancy interactions in graphene. We demonstrate that the crack-tip stress field of an existing crack in graphene can be effectively tailored (reduced by over 50% or increased by over 70%) by the strategic placement of atomic vacancies of varied shapes, locations, and orientations near its tip. The crack-vacancy interactions result in a remarkable improvement (over 65%) in the fracture strength of graphene. Moreover, at reduced stiffness of graphene, due to a distribution of atomic vacancies, a drastic difference (similar to 60%) was observed between the fracture strengths of two principal crack configurations (i.e. armchair and zigzag). Our numerical simulations provide a remarkable insight into the applicability of the well-established continuum models of crack-microdefect interactions for the corresponding atomic scale problems. Furthermore, we demonstrate that the presence of atomic vacancies in close proximity to the crack-tip leads to a multiple-stage crack growth and, more interestingly, the propagating cracks can be completely healed even under a significantly high applied tensile stress level (similar to 5 GPa). Our numerical experiments offer a substantial contribution to the existing literature on the fracture behavior of two-dimensional nanomaterials. (C) 2017 Elsevier B.V. All rights reserved.