Fracture of low-dimensional nanomaterials

We found different failure mechanisms and mechanical properties for single-walled carbon nanotubes (SWCNTs) when subjected to electric fields and that subjected to tensile load by quantum mechanics calculations. The electric field induced breaking in SWCNT begins from the outmost carbon atomic layers while the tensile load breaks the nanotube near its middle. When a tube is tensioned in an electric field, the critical tensile strength of the tube decreases significantly with increasing intensity of the electric field. It is interesting to be shown that a piece of graphene sheet formed by unwrapping the SWCNT can also be stretched up to 2.5% by applied electric field and fractured at it edges. We also studied the mechanical response and structural evolution of graphene with topological line defect under tensile strain by using first-principles calculations. We studied the superelongation and fracture of carbon nanotubes at high temperatures by molecular dynamics simulations, and found that the nearly simultaneous activation and wide distribution of a large number of defects near the elastic limit play a key role in impeding the formation of localized predominant instability and facilitating large tensile elongation of carbon nanotubes at high temperature.