Crystals of covalently bonded carbon nanotubes: Energetics and electronic structures

Structure and stability of hexagonally polymerized carbon nanotube solids are investigated using a generalized tight-binding molecular-dynamics scheme. The stable structures show internanotube connectivity via the 2+2 and 2+4 cycloaddition process. Calculated electronic density of states indicates that the studied materials have semiconducting or insulating properties depending on the type of internanotube connectivity in a system containing atoms with sp(2) and sp(3) bondings. We also predict the existence of a nanotube clathrate form.