Elastic properties of single-wall nanotubes

We report results of theoretical studies on the elastic properties of singl e-wall nanotubes of the following compositions: C, BN, BC3, BC2N, and C3N4 These studies have been carried out using a total-energy, non-orthogonal, t ight binding parametrisation which is shown to provide results in good agre ement both with calculations using higher levels of theory and the availabl e experimental data. Our results predict that of all types of nanotubes con sidered, carbon nanotubes have the highest Young's modulus. We have conside red tubes of different diameters, ranging from 0.5 to 2 nm, and find that i n the limit of large diameters the mechanical properties of nanotubes appro ach those of the corresponding flat graphene-like sheets.