The effect of various defects and boundary structures upon the low-energy electronic properties of conducting zig-zag and armchair carbon nanotubes was considered. The tight-binding model of the conduction bands was mapped exactly onto simple lattice models consisting of two uncoupled parallel chains. Imperfections such as impurities, structural defects, or caps could be easily included in the effective lattice models, allowing a detailed physical interpretation of their consequences. The method was quite general and could be used to study a wide range of possible imperfections in carbon nanotubes. The electron-density patterns expected from scanning tunneling microscopy of half-fullerene caps and typical impurities in the bulk of a tube (Stone-Wales defect and a single vacancy) were obtained.

Lattice Defects and Boundaries in Conducting Carbon Nanotubes. S.A.Reyes, A.Struck, S.Eggert: Physical Review B, 2009, 80[7], 075115