Theory of ${\mathrm{B}}_{\mathrm{2}}\mathrm{O}$ and ${\mathrm{B}\mathrm{e}\mathrm{B}}_{2}$ Nanotubes: New Semiconductors and Metals in One Dimension

Theory of $B_{2} O$ and ${B e B}_{2}$ Nanotubes: New Semiconductors and Metals in One Dimension

Peihong Zhang and Vincent H. Crespi

Phys. Rev. Lett. 89, 056403 – Published 15 July 2002

Abstract

We describe two new boron-based nanotubes: $B ︀_{2} O$ and $BeB ︀_{2}$ . Both are isoelectronic to graphite, have reasonable curvature energies, and have already been made in their bulk planar forms. The lowest energy allotrope of planar single-layer $B ︀_{2} O$ is a semiconductor with a moderate band gap. The local density approximation band gap of the corresponding $(3, 0)$ $B ︀_{2} O$ nanotube [similar in size to $(9, 0)$ carbon nanotube tube] is direct and around 1.6 eV, within a range inaccessible to previous $C$ or $B N$ nanotubes. Single-layer $BeB ︀_{2}$ has a fascinating structure: the $B e$ atoms rest above the boron hexagonal faces, nearly coplanar to the boron sheet. The unusual $K$ -point $π - π^{*}$ Fermi-level degeneracy of graphite survives, while a new nearly pointlike Fermi surface appears at the $M$ point. As a result, $BeB ︀_{2}$ nanotubes are uniformly metallic.