Fracture behavior of graphene with intrinsic defects and externally introduced defects

Abstract

Introducing and regulating defects to prepare functional graphene has become a research hotspot. However, most studies focus on the mechanical properties of functional graphene or the influence of a single defect, which cannot reflect the influence of multiple coupled defects on mechanical properties. In this study, molecular dynamics methods were used to investigate the fracture behavior of graphene under the coupled effects of intrinsic defects such as vacancies, cracks, and topological defects, as well as external introduced defects such as epoxy groups and hydroxyl groups. The results showed that the fracture behavior of graphene is strongly related to the defects' type, concentration, and functionality. Under the same conditions, the epoxy group has the strongest leading effect on fracture, followed by cracks, Stone-Wales topological defects, and hydroxyl groups. Based on the tensile simulation of defect-ordered graphene, the critical relative concentrations and functionalities of different defect types leading to fracture were further quantified and validated using an amorphous distribution model. In addition, the fracture mode dominated by epoxy groups is related to its functionality. Excessive or insufficient functionality will exhibit strong brittle fracture characteristics, and when the functionality is at a certain threshold, it will exhibit obvious ductile fracture characteristics; while hydroxyl-dominated fracture presents brittle mode. Finally, the coupled fracture mechanism was analyzed from the aspects of bonding characteristics and system energy. The research results can provide reference and reference for the theoretical research and technological development of graphene.