THE EQUILIBRIUM STRUCTURES OF GIANT FULLERENES - FACETED OR SPHERICAL SHAPE - AN AB-INITIO HARTREE-FOCK STUDY OF ICOSAHEDRAL C-240 AND C-540

Ab initio self-consistent field (SCF) Hartree-Fock (HF) geometry optimizations employing minimal basis indicate the existence of a single, faceted polyhedral equilibrium structure in the potential energy surface of C(240)and C-540. These results are in contrast with recent divide-and-conquer density functional predictions for C-240 which found a lowest energy isomer of spherical nature. The present theoretical predictions are compared with available experimental information on these giant fullerenes. The C-540 calculation in this work involves 2700 basis functions and is the largest Hartree-Fock calculation reported to date.