Ideal torsional strengths and stiffnesses of carbon nanotubes

The ideal torsional strengths of a class of carbon nanotubes, and the torsional stiffnesses of all carbon nanotubes are computed using a novel combination of an ab initio electronic structure total energy technique and a physically motivated scaling form. The specific torsional strengths of multi-walled tubes are predicted to exceed those of steel by approximately a factor of 20. Closed-form expressions that bound the torsional stiffnesses are also presented. The predictions of the theory give excellent agreement with available experimental data.