Ab initio calculations for a hypothetical material: Silicon nanotubes

Electronic and structural properties of a hypothetical material, silicon na notubes, are examined through first-principles calculations based on densit y functional theory. Even considering that Si nanotubes have never been obs erved, this paper attempts to establish the theoretical similarities betwee n Si and C, like band structures and density of states, as well as the main differences, especially associated with cohesive energies. The band-struct ure calculations for silicon nanotubes show that, similar to carbon structu res, depending on their chiralities, they may present metallic (armchair) o r semiconductor (zigzag and mixed) behaviors.