  Shapes and energies of icosahedral fullerenes are studied on an atomically
detailed level. The numerical results based on the effective binary
carbon-carbon potential are related to the theory of elasticity of crystalline
membranes with disclinations. Depending on fullerene size, three regimes are
clearly identified, each of them characterized by different geometrical
properties of the fullerene shape. For extremely large fullerenes (more than
about 500000 atoms), transition of fullerene shapes to their asymptotic limit
is detected, in agreement with previous predictions based on generic elastic
description of icosahedral shells. Quantum effects related to delocalized
electrons on the fullerene surface are discussed and a simple model introduced
to study such effects suggests that the transition survives even in more
general circumstances.
