Brittle and Ductile Behavior in Carbon Nanotubes

Large-scale molecular dynamics simulations were used to study the response of carbon nanotubes to a tensile load. Plastic or brittle behaviors can occur depending upon the external conditions and tube symmetry. All tubes are brittle at high strain and low temperature, while at low strain and high temperature armchair $(n,n)$ nanotubes can be completely or partially ductile. In zigzag $(n,0)$ tubes ductile behavior is expected for tubes with $n<14$, while larger tubes are completely brittle. In both cases the curvature determines the mechanical response.