Energetics of bent carbon nanotubes

Several junctions between different nanotubes have been constructed which preserve the C sp2 honeycomb lattice with the sole insertion of a pentagon and a heptagon. This construction bends the structure at an angle that depends on the distance between the pentagon and heptagon. The atomic structure of these systems was optimized with empirical interatomic potentials. The nanotubes on both sides of the junctions were treated as infinitely long. Local σ+π electron densities of states were computed locally in the interfacial region with a tight-binding Hamiltonian. From this, the electron energy of the junctions was computed and compared to that of the separated nanotubes. It is found that the energy of a pentagon-heptagon defect in the graphitic tubular network is around 6 eV.