Structure, chirality, and formation of giant icosahedral fullerenes and spherical graphitic onions

We describe the topology, structure, and stability of giant fullerenes exhibiting various symmetries (I, I_h, D_2h, T). Our results demonstrate that it is possible to create two new families of nested "crural" icosahedral (I) fullerenes namely C₂₆₀@C ₅₆₀@C₉₈₀@C₁₅₂₀@ ... and C₁₄₀@C ₃₈₀@C₇₄₀@C₁₂₂₀@ ..., which exhibit interlayer separations of ca. 3.4 Å. These chiral fullerenes are thought to possess metalliclike conduction properties. We discuss in detail the transformation of polyhedral graphitic particles into quasispherical nested giant fullerenes by reorganization of carbon atoms, which result in the formation of additional pentagonal and heptagonal carbon rings. These "spherical" structures are metastable and we believe they could be formed under extreme conditions, such as those produced by high-energy electron irradiation. There is circumstantial experimental evidence for the presence of heptagonal rings within these spherical fullerenes.