Geometric Structure And Electronic Structure Of Fullerene Derivatives

Geometric and electronic properties of hydrofullerenes C60H6, metal-carbon encaged fullerene Sc2C2@C84 and C58Si2 have been studied using the density functional theory(DFT) at BLYP level with dnp basis sets. The Sc2C2 cluster was found to be stable in the cage structure, while the volume of the cage expands slightly. After Sc2C2 cluster was encaged, the degeneracy of energy splits, and HOMO-LUMO energy gap becomes smaller than that of the pure C84 cage which suggests Sc2C2@C84 has higher reactivity than C84 cage. The electronic structure of Sc2C2@C84 is formally described as (Sc2C2)+1@(C84)-1 as a result of the charge transfer ing from Sc2C2 cluster to C84 cage. To the hydrofullerenes C60H6, the volume of the cage was found to expand slightly after six hydrogen atoms were added to the outside of the pure C60 molecule, and the C atoms which connect with hydrogen atoms some pop out. Because of these six hydrogen atoms, the degeneracy of energy splits, while the HOMO-LUMO energy gap is very close to that of the pure C60 cage, just by 0.03 eV smaller . The electronic structure of C60H6 could be described as (H6)+1@(C60)-1, as a result of the charge transferring from six hydrogen atoms to the C60 cage. To C58Si2, the geometric structure with which the two Si atoms are located at the diagonal positions of a hexagonal ring (called C58Si2-6 below) is 0. 11eV lower in energy than that with which the two Si atoms are locatedat the diagonal positions of a pentagonal ring (called C58Si2-5 below). C5gSi2-6 can keep the geometry of Ceo except for the region near Si atoms. The degeneracy of the energy levels is removed because of Cs symmetry and the energy gap between HOMO-LUMO becomes smaller than that of C60. Each Si atom loses 1. 122e, which is mainly transferred to the three neighboring C atoms. It makes the Si-C bonds polarized and increases the binding energy.