Ab initio study of single-wall BC2N nanotubes

First-principles calculations based on a density functional theory were carried out to investigate electronic properties of BC2N nanotubes. It was found that the strain energy of the BC2N nanotube depends on the diameter but independent of the chirality of the tube. The electronic properties, however, are closely related to both the diameter and chirality of the tube. Generally, all BC2N nanotubes, except for a few with very small diameters, are direct gap semiconductors. Both the top valence band and the bottom conduction band are formed by carbon p orbitals normal to the tube surface.