Pentagon-heptagon defect

Fig. 12.2 Molecular orbital energies and shapes of the HOMO and LUMO for graphene without defects (Gl), pentagon-octagon defects (G2 and G3), and pentagon-heptagon defect (G4) and...

Because of the speeial atomie arrangement of the earbon atoms in a carbon nanotube, substitutional impurities are inhibited by the small size of the carbon atoms. Furthermore, the serew axis disloeation, the most eommon defeet found in bulk graphite, is inhibited by the monolayer strueture of the Cfj() nanotube. For these reasons, we expeet relatively few substitutional or struetural impurities in single-wall earbon nanotubes. Multi-wall carbon nanotubes frequently show bamboo-like defects associated with the termination of inner shells, and pentagon-heptagon (5 - 7) defects are also found frequently [7]. 

The trigonal connectivity leads not only to hexagons but enables the incorporation of triangles, pentagons, heptagons and larger cyclic structures as local defects into the basic honeycomb structure. A consequence of these defects is the strong localization of double bonds... 

Considering the above experimental and theoretical evidences of the structural stability of hexagonal systems with 5 7 defects, this theoretical note aims to investigate the topological, wave-like mechanisms leading the diffusion (or annihilation) of pentagon-heptagon pairs. 

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