Jahn-Teller distortion of ionized and excited carbon nanotubes

摘要

Due to their rotational (C_n) symmetry, neutral zigzag and armchair type nanotubes possess doublydegenerate orbitals. As the energies of highest occupied molecular orbital and lowest unoccupiedmolecular orbital are usually different, neutral nanotubes exhibit a nondegenerate ground state.Ionized or excited forms of these tubes, however, may undergo Jahn–Teller distortion if degenerateorbitals show up in the vicinity of the Fermi level. Theoretical calculations in a simpleone-eletron-per-site model show that the Jahn–Teller distortion energies are in order-of-magnitudeof 0.1 eV for short pieces of tubes, and are associated with a significant geometry change.Distortions tend to diminish quickly with increasing tube length, except if multiple ionizations areconsidered.