DENSITY-FUNCTIONAL CALCULATIONS OF ELECTRONIC AND STRUCTURAL-PROPERTIES OF SMALL FULLERENE TUBULES

Results of first-principles density-functional calculations of electro nic properties of structure-optimized isolated fullerene tubules are r eported. Special emphasis is put on structural properties of the small est tubules one can think of, and on whether they are metallic or semi conducting. We find that the smallest tubules have markedly different structural and electronic properties from those of a folded graphite s heet, a fact that distinguishes them from the larger, more graphite-li ke tubules. As compared to a folded sheet of graphite, the smallest tu bules have large structural relaxations which become progressively sma ller as the diameter of the tubule increases. The electronic structure s of the smallest tubules are modified by significant interaction acro ss 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 tu bules. For the smallest, the (1, 0) tubule, the structural relaxations lead to a semiconducting behaviour with a band pp of around 1 eV.