Multi-walled carbon nanotube

A carbon nanotube comprising several nested graphitic walls. Each shell can have its own wrapping indices; their difference alone is not a structural defect.

An area-based estimate treating each nanotube shell as a graphene cylinder. For graphene atomic area density $n_s$ and shell radii $r_j$, the carbon count per axial length is $N_C/\ell =2\pi n_s{\sum }_j{r}_j$. Defects and partial shells change the estimate.