Ultra-Fast Dynamics In Electronically Excited Nanotubes: Time-Dependent Density Functional Approach

Because of extreme mechanical and electronic performance, carbon nanotube is promising material for application in nanotechnology. Currently formed nanotubes contain structural defects and impurities, which may cause degradation of nanotubes. Therefore, influence of defects and impurities on mechanical and electronic properties of nanotube should intensively be investigated. Furthermore, defect control will be an important technology in future nanotube applications. In this talk, we provide our recent first principles simulations on ultra fast dynamics in nanotubes triggered by electronic excitation. We first demonstrate that electronic excitation is useful to repair defected nanotube being subjected to heat treatment. Second, we show optical excitation can be a useful tool to detect particular kind of defects in nanotube, i.e. Stone-Wales type defects. We have performed molecular dynamics (MD) simulations based on of local density approximation (LDA) of the density functional theory (DFT) with use of plane-wave basis set and pseudopotentials. We adopted time-dependent LDA in order to perform MD simulation under electronic-excitation, where the time-dependent Kohn-Sham equation is solved to monitor time-evolution of electron wave functions. The details of this method are shown by Sugino and Miyamoto.