Dislocations, Plasticity, and Strain Hardening in Carbon Nanotubes

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Dislocations, Plasticity, an Strain Hardening in Carbon NanotubesD. C. ChrzanDepartment of Materials Science and EngineeringUniversity of CaliforniaBerkeley, CA 94720-1760AbstractCarbon nanotubes display unusually high tensile strengths and stiffnesses, and breaking stresses as high as 30 GPa have been reported. While the elastic properties of carbon nanotubes are well understood, the plastic properties of carbon nanotubes remain unsettled. Intriguingly, carbon nanotubes are expected to deform plastically through the nucleation of dislocation dipoles (Stone-Wales defects), the dissociation of these dipoles, and the subsequent motion of the dislocations. Estimates of the formation energy for Stone-Wales defects vary widely, perhaps because their formation energy is influenced by elastic interactions between the defects. We will use elasticity theory solutions for periodic dislocation arrays to analyze defect formation energies obtained from density functional theory based total energy methods. This analysis will yield core radii for the dislocations and ultimately, a transferable theory of dislocations in nanotubes. This theory can then be applied to model plasticity in carbon nanotubes under a variety of loading conditions.