Elastic Properties of C and B x C y N z Composite Nanotubes

We present a comparative study of the energetic, structural, and elastic properties of carbon and composite single-wall nanotubes, including BN, ${\mathrm{BC}}_{3}$, and ${\mathrm{BC}}_{2}\mathrm{N}$ nanotubes, using a nonorthogonal 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.