Stacking characteristics of graphene shells in carbon nanotubes

Intershell spacings between carbon nanotubes <(d)over cap (002)> ranging from 3.59 Angstrom to 3.62 Angstrom, with an uncertainty of +/- 0.06 Angstrom, are deduced by using the in-plane C-C bonding length in the graphene hexagonal network as an internal calibration standard for the digital image analysis of TEM lattice images. These large <(d)over cap (002)> values imply weak intershell correlation between carbon atoms on adjacent tubules. By using the measured <(d)over cap (002)> values and the finite number of possible nanotubes, a determination of the chiral vector is made for two shells within a multiwall nanotube. The connection between constraints on <(d)over cap (002)> and the self-assembly of multilayer carbon nanotubes is discussed.