First-principles studies on pure and doped C32 clusters

On the basis of first-principles calculations, pure and doped C-32 clusters are studied. Among the nine structural isomers, the fullerene structure with Dg symmetry is found to be the most stable. Due to the small size of the C-32 cage, Li and Na atoms can be stably encapsulated, while K and Be atoms are not. On encapsulation, the bond length of the H-2 molecule is reduced while the vibration frequency is increased. Substitutional doping is more favourable than endohedral doping for Si atoms. Because of the sp(2)-bonding features of C atoms, the Si atom is also threefold coordinated in substitutional doping; however, the existence of one dangling bond in the Si atom makes this doped heterofullerene reactive at the Si site, and H termination can produce substantial energy gain.