Geometrical structures and electronic properties of AlN fullerenes : A comparative theoretical study of AlN fullerenes with BN and C fullerenes

We present a comparative theoretical study of AlN fullerenes with BN and C fullerenes using both the Hartree-Fock and density functional theories. The smallest (AlN)₁₂ cage is proved to be energetically more favorable than its monoring and graphitic sheet isomers. This structure is expected to be reasonably stable, once it is formed, as indicated by its large HOMO-LUMO gap, although it is thermodynamically less favorable than the corresponding (BN) ₁₂ and C₂₄ fullerenes. A similar case was also observed for larger (AlN)₃₆ fullerene. The possibility of the existence of AlN nanotubes was also explored by inspecting the geometrical change of a ideal (AlN)₃₀ nanotube with opened ends during the geometrical optimization. Our results show that the tube tends to close its ends and prevent further growth of the tube, which explains the present experimental difficulty in synthesizing single walled AlN nanotubes. © The Royal Society of Chemistry 2005.