Abstract
Optical properties of three kinds of zigzag (5,0), (13,0), and (9,0) single-walled carbon nanotubes (SWCNTs) are studied using an approximate quantum mechanical method named complete neglect of differential overlap, which distinguishes basis atomic orbitals with different azimuthal $l$ quantum numbers (CNDOL). This method models the electron energy transitions and excited state charge distributions through a configuration interaction of singly (CIS) excited determinants allowing the direct understanding of properties related with the total electronic wave function of nanoscopic systems, projecting a reliable quantum mechanical understanding to real life objects. The finite SWCNT's structures were obtained by replicating the unit cells of periodic SWCNTs and saturating the edge dangling bonds with hydrogens. The unit cell was previously relaxed using standard density functional theory methods. The behavior of these SWCNTs were interpreted in the framework of the CNDOL scheme by increasing the lengths of the tubes above 3 nm. As the nanotubes grow in length, the position of excited states for each SWCNT evolve differently: in contrast with (9,0) SWCNT, which exhibits favorable conditions for photoexcitation, the (13,0) and (5,0) SWCNTs do not show a lowering of the lowest excited states. This behavior is discussed by taking into account electron---electron interactions as considered in the framework of the CIS procedure. Furthermore, the (13,0) and (5,0) SWCNTs present forbidden transitions for the lowest excitations and its first dipole-allowed transitions are at 0.9--1.0 and 1.4--1.6 eV, respectively. In contrast, (9,0) SWCNT allows excitations by photon at less than 0.4 eV as the length of the nanotube tends to infinite. Excitons appear more bounded, energetically and spatially, in the (13,0) than in the (9,0) and (5,0) SWCNTs.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.