Density-functional calculations of electronic and structural properties of small fullerene tubules

Abstract

Results of first-principles density-functional calculations of electronic properties of structure-optimized isolated fullerene tubules are reported. Special emphasis is put on structural properties of the smallest tubules one can think of, and on whether they are metallic or semiconducting. We find that the smallest tubules have markedly different structural and electronic properties from those of a folded graphite sheet, a fact that distinguishes them from the larger, more graphite-like tubules. As compared to a folded sheet of graphite, the smallest tubules have large structural relaxations which become progressively smaller as the diameter of the tubule increases. The electronic structures of the smallest tubules are modifed by significant interaction across the interior of the tubule. This leads to an overall broadening of 2–3 eV of the electronic density of states compared with the larger tubules. For the smallest, the (1, 0) tubule, the structural relaxations lead to a semiconducting behaviour with a band gap of around 1 eV.