Elastic Properties of Single-Wall Nanotubes

We report results of theoretical studies on the elastic properties of single-wall nanotubes of the following compositions: C, BN, ${BC}_3$, ${BC}_2{N}$ and ${C}_3{N}_4$. These studies have been carried out using a total energy, non-orthogonal tight-binding parametrisation which is shown to provide results in good agreement both with calculations using higher levels of theory and the available experimental data. Our results predict that of all types of nanotubes considered, carbon nanotubes have the highest Young's modulus. We have considered tubes of different diameters, ranging from 0.5 to 2~nm, and find that in the limit of large diameters the mechanical properties of nanotubes approach those of the corresponding flat graphene-like sheets.