Anurak Udomvech. The geometry and electronic structure of nanotubes and their application as charge storage and transport devices . Master's Degree(Physics). Mahidol University. : Mahidol University, 2003.
The geometry and electronic structure of nanotubes and their application as charge storage and transport devices
Abstract:
Carbon nanotubes are a seamlessly rolled-up single shell of graphene sheet that have a diameter of a few nanometers. This research focused on single-wall carbon nan-otubes (SWNTs) that have a zigzag shape. The geometry and electronic structure of open- and closed-end (9,0) zigzag nanotubes was studied. The dependence of geometrical parameters, the HOMO-LUMO gaps and charge distribution on the SWNTs length were investigated using molecular mechanics, several ab-initio and semi-empirical quantum computational techniques. It was found that the geometry of SWNTs is effected by varying tubule length and if the tube ends are open and capped. The results of energy gap suggest that both open- and closed-end finite-sized SWNTs are a semiconductor, and capping also strongly effects the electronic structure of SWNTs. It was found that the electronic charge density slightly accumulates at the two ends of closed SWNTs. Li ion penetration through the side wall of SWNTs was studued by density functional methods. Li ion interaction potential inside the SWNTs had a double-well shape. It was found that a Li ion should not simply pass through a nanotube wall due to a high potential barrier at the wall. Thus, Li ion would penetrate through the hexagon rather than bonding topology due to a very large difference of potenial barriers. Charge transfer from SWNT to Li ion was observed.