Abstract
Understanding the effect of defects on mechanical responses and failure behaviors of a graphene membrane is important for its applications. As examples, in this paper, a family of graphene with various 5–8–5 defects are designed and their mechanical responses are investigated by employing molecular dynamics simulations. The dependence of fracture strength and strain as well as Young’s moduli on the nearest neighbor distance and defect types is examined. By introducing the 5–8–5 defects into graphene, the fracture strength and strain become smaller. However, the Young’s moduli of DL (Linear arrangement of repeat unit 5–8–5 defect along zigzag-direction of graphene), DS (a Slope angle between repeat unit 5–8–5 defect and zigzag direction of graphene) and DZ (Zigzag-like 5–8–5 defects) defects in the zigzag direction become larger than those in the pristine graphene in the same direction. A maximum increase of 11.8% of Young’s modulus is obtained. Furthermore, the brittle cracking mechanism is proposed for the graphene with 5–8–5 defects. The present work may provide insights in controlling the mechanical properties by preparing defects in the graphene, and give a full picture for the applications of graphene with defects in flexible electronics and nanodevices.
Highlights
Understanding the effect of defects on mechanical responses and failure behaviors of a graphene membrane is important for its applications
By employing aberration corrected transmission electron microscopy (ACTEM), they investigated the different structural permutations of the tetravacancy defect[13], and found that the structures depends on the specifics of vacancy creation
By employing nonequilibrium molecular dynamics simulations, divacancy was reconstructed by Liang et al.[22], and the main manner for forming that structure is found, i.e. the
Summary
The equilibrium is realized by a conjugate-gradient algorithm, and a simulation with isothermal-isobaric (NPT) ensemble is carried out for 10 ns to eliminate the inner stress of graphene with defects, followed by the simulation with microcanonical ensemble (NVE) for another 10 ns. Tension load is applied to the graphene sheet in the armchair or zigzag direction with a strain rate of 0.0004 ps−1 and the increment every 1 ps. The thickness 3.4 Å is employed to compute the atomic stress in graphene sheet[35]. The calculation of the Young’s modulus, the fracture strain, the fracture strength, tensile strength, and ultimate strain are following references[30,36,37]
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