Molecular Dynamics Simulation of Elastic Properties and Fracture Behavior of Single Wall Carbon Nanotubes with Vacancy and Stone-Wales Defect

摘要

Perfect carbon nanotubes are exceptionally strong nanostructures with fascinating mechanical characteristics. But the presence of crystal defects like Stone-Wales defects or vacancies degrade their mechanical properties to a large extent. The effects of the presence of a single Stone-Wales defect or a single vacancy defect on the elastic properties and the fracture pattern of a single-walled carbon nanotube (SWCNT) are investigated by molecular dynamics (MD) simulation. We considered three samples of SWCNT, one each of chiral, armchair and zigzag type. In all the three samples, significant changes are observed compared to a defect-free tube. A defective chiral (10,6) tube shows more stability under stretched condition compared to the armchair (7,7) or the zigzag (10,0) tube as revealed from the energy differences between defective and defect-free tubes at different stages of deformation. Fluctuation of energy differences for higher strain values for the same defect orientation is observed to be most pronounced in the case of a zigzag tube and hence shows a less stable configuration than the other two tubes. The fracture pattern in each case is modelled and shows that defects play a major role in the breaking mechanism of a SWCNT. Also the differences in fracture modes of chiral and achiral tubes prove the dependence of their mechanical behavior on chirality.