Structure and energetics of single and multilayer fullerene cages

Minimum energy structures for large carbon cages are investigated using realistic atomic potentials. Above a critical size of ∼6000 there is a stability crossover from single to multilayer cages. The lowest energy atomic configuration of a cage of any size consists only of hexagons and pentagons and is polyhedral in shape. Lowest energy defects involve either rearrangements between pentagons and hexagons or 5-7-5 triplets. Simulated transmission electron microscopy images show that a polyhedral onion appears spheroidal when viewed along its highest symmetry axis, and polyhedral when viewed from a more general direction.