Stability and Electronic Properties of Bismuth Nanotubes

Recently fabricated double-walled bismuth nanotubes were the first elemental nanotubes with clearly expressed layered structure analogous to carbon nanotubes. Here the results from quantum-mechanical density-functional tight-binding (DFTB) calculations are presented for Bi nanotubes of experimentally observed diameters. The calculations uncover the nature of the experimentally observed shape of bismuth nanotubes as an interplay between relatively low strain energies of Bi nanotubes and rather strong van der Waals interaction between the layers. They evidence the stability of the hexagonal prismatic morphology for double-walled zigzag nanotubes. Band structure calculations reveal that the Bi nanotubes should be semiconducting with the band gap around 0.5 eV.