Optical band gaps of zigzag CNTs

We report optical transitions of zigzag carbon nanotubes calculated by Fermi's golden rule. The electronic band structure and density of states have been simulated using density functional theory as implemented in the wien2k code. E-ss (s = 1, 2) of CNTs (n, 0) (n = 4, 8) for parallel and perpendicular to the tube axis polarizations have been calculated precisely. By applying parallel to the tube axis polarization, CNTs (8, 0) shows higher optical band gaps rather than CNT5 (4, 0). Moreover, calculated reflection spectra show polarizations perpendicular to the tube axis with higher peaks. (C) 2016 Elsevier GmbH. All rights reserved.