Band Gaps of Single-Walled Carbon Nanotubes: A Computational Study

Abstract

I studied the electronic band structure of carbon nanotubes through computer simulations using quantum molecular dynamics. I demonstrated that band gap energies can be "tuned" by the application of external tensile strain. Tunable nanotubes have the potential to revolutionize the world of technology. I obtained a phase diagram for smaller diameter carbon nanotubes and compared my data to the phase diagram based on the graphene model and found that they did not follow the predicted pattern where one third of all nanotubes are conducting. Using the Fermi-Dirac distribution, I calculated the band gap energies for each of the nanotubes I successfully modeled. Further, I looked for a correlation between the band gap energies and the diameters and discovered that contrary to expectations, smaller diameter nanotubes did not have energies inversely proportional to diameters due to large curvature effects. Finally, I measured band gap energies as a function of applied tensile stress; the band gaps in conducting nanotubes increased with applied tensile stress, whereas the band gaps in semiconducting nanotubes decreased. These results are in accord with theoretical predictions.