Elastic Properties of C and BxCyNz Composite Nanotubes
  We present a comparative study of the energetic, structural and elastic properties of carbon and composite single-wall nanotubes, including BN, BC3 and BC2N nanotubes, using a non-orthogonal tight-binding formalism. Our calculations predict that carbon nanotubes have a higher Young modulus than any of the studied composite nanotubes, and of the same order as that found for defect-free graphene sheets. We obtain good agreement with the available experimental results. 
E. Hernandez, C. Goze, P. Bernier and A. Rubio