Defect states in carbon nanotubes and related band structure engineering: A first-principles study

Electronic structures of faulted nanosystems are of particular technological relevance because realistic large scale synthesis of nanostructures inevitably leads to defects of one form or the other. In this work, we determine the atomic and electronic structures of carbon nanotubes (CNTs) with two of the major types of defects using first-principles pseudopotential-based density functional theory calculations: (i) substitution with other atoms, and (ii) defects formed by removal of C atoms in the otherwise perfect honeycomb graphene network. We find that doping with B or N atom at different carbon sites of a CNT gives a simple shift in the Fermi energy and a nonmagnetic state. We evaluate the energy cost associated with the formation of nanotube interconnects by introducing a pair of heptagon and pentagon at the junction of two nanotubes and discuss how different defects can lead to band structure control. Further, a line defect for faulted CNTs is discussed for CNTs, which exhibit stronger one-dimensiona...