Chirality Effects in Atomic Vacancy-Limited Transport in Metallic Carbon Nanotubes

We use first principles density functional theory combined with nonequilibrium Green's function technique to investigate the electronic and transport properties of metallic armchair and zigzag carbon nanotubes (CNTs) with different kinds of multivacancy defects. While the existence of a small band gap in pristine zigzag (12,0) CNTs lowers its conductance compared to pristine armchair (7,7) CNTs, transport properties in the presence of multi (hexa)-vacancy are superior in the former nanostructure, that is more sensitive to defect size and topology than the latter. In addition, in the zigzag structures hexavacancy nanotubes have higher conductance than divancancy nanotubes, which is due to the presence of midgap states that reduce the transmission gap and enhance the conductance.