Simulated annealing of carbon clusters

A semiempirical many-body potential [J. Tersoff, Phys. Rev. Lett. 61, 2879 (1988)] has been used to model carbon clusters (${\mathit{C}}_{\mathit{n}}$) in the size range 50≤n≤72. Ground-state geometries are identified by simulated annealing. Our results show that, for these sizes, all the structures of low energies are hollow spheres, with nearly graphitic atomic arrangement. The n dependence of the cohesive energy singles out n=60 and n=70 as particularly stable structures. We investigate the effect of vibrations (zero-point energy) and temperature on the relative stability of different cluster sizes.