Concentric carbon structures

We develop a topological explanation of turbostratic stacking and short-range order in multishell nanotubes and fullerene onions through the analysis of steric constraints. A proposed nanotube structure gives good Rietveld x-ray-diffraction refinement of well-annealed samples. We show that each layer in the nanotubes has preferentially a left or right unique helix and stable onions a highly distorted hexagonal array with constant interlayer spacing.