Zero-field-splitting in triplet-state nanotubes

Zero-field-splitting parameters D and E are evaluated for various excited triplet carbon nanotubes. For cylindrical ( C n v ) tube geometries only parameter D is nonzero. Parameter E is nonvanishing either for chiral tubes which lack C n v symmetry, or for those excited states of achiral tubes, which loose C n v symmetry due to Jahn–Teller distortion. The splitting is found to decrease with increasing tube length and tube diameter. The decay is fast and tends to zero if the excitation affects surface-type states, while D approaches a nonzero limit if the open shell orbitals are of bulk character.