Kinetic Monte Carlo Simulations of the Response of Carbon Nanotubes to Electron Irradiation

Irradiation is increasingly used nowadays to tailor the mechanical and electronic properties of carbon nanotubes. As the complete understanding of the response of nanotubes to irradiation is still lacking, we have implemented the kinetic Monte Carlo method with Bortz-Kalos-Lebowitz–algorithm in a simulation code which enables modeling the behavior of irradiated nanotubes on macroscopic time scales. Within our model, the paths and energy barriers for the diffusion of irradiation-induced defects are obtained from density-functional-theory–based calculations. We have applied the model to single-walled nanotubes subjected to electron irradiation in a transmission electron microscope at different temperatures. In perfect agreement with the experiments, our simulations indicate that at temperatures higher than 300 °C the annihilation of defects is efficient enough for almost perfect in situ self-healing of nanotubes. Our results on the irradiation doses needed to cut a single-walled nanotube with an electron beam are also similar to the experimental values. We also found that, surprisingly, for a certain range of relatively low temperatures (about 130–230 °C) the temperature increase can have a negative effect on the self-healing.