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Stress-induced annihilation of Stone–Wales defects in graphene nanoribbons

Stress arising from structural or thermal misfit impacts the reliability of graphene-related devices. The deformation behaviour of graphene nanoribbons (GNRs) with Stone–Wales defects under stress studied by molecular dynamics shows that nearly all the SW defects annihilate via inverse rotation of C–C bonds. The fracture stress of defective GNRs is comparable to that of perfect ones and similar to mechanical annealing observed from bulk metals. It is a competition between bond rotation and fracture and depends on the strain rate and temperature. At a lower strain rate, such as 10−5 ps−1, the rotation velocity of C–C bonds of 4.2 Å ps−1 is three orders of magnitude larger than the velocity of the collective movement of atoms (1.2 × 10−3 Å ps−1). There is enough time for the C–C bond rotation to respond to the external load, but it becomes more difficult at higher strain rates. This stress-induced SW defect annihilation can be enhanced at higher temperatures because of enhanced exchange of atomic momentum and energy. The results reveal the dominant influence of SW defects on the mechanical properties of two-dimensional materials.