Jahn–Teller distortion of ionized and excited carbon nanotubes

Abstract

Due to their rotational (C(n)) symmetry, neutral zigzag and armchair type nanotubes possess doubly degenerate orbitals. As the energies of highest occupied molecular orbital and lowest unoccupied molecular 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 degenerate orbitals show up in the vicinity of the Fermi level. Theoretical calculations in a simple one-eletron-per-site model show that the Jahn-Teller distortion energies are in order-of-magnitude of 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 are considered.