Search for more stable [C.sub.58][X.sub.18] isomers: Stabilities and electronic properties of seven-membered ring [Csub.58][X.sub.18] fullerene derivatives (X = H, F, and Cl)

A systematic density functional theory (DFT) calculations is performed on the stabilities and electronic properties of two different structures [Csub.58][X.sub.18] and [C.sub.58][X.sub.1], where X = H, F, and Cl. It is seen that the large energy gaps between the highest occupied molecular orbitals and the lowest unoccupied molecular orbital and the aromatic character possess high stabilities.