Geometric and electronic structures of metal-substitutional fullerene $C59Sm$ and metal-exohedral fullerenes $C60Sm$

The geometric and electronic structures of metal-substituted fullerene $C59Sm$ and exohedral fullerenes $C60Sm$ are studied using the density-functional theory. The geometric optimization shows that the replacement of a C atom with a Sm in $C60$ yields a stable substitutionally doped fullerene $C59Sm$⁠, and among the five possible optimized geometries for $C60Sm$⁠, the most favorable exohedral sites are above the center of a hexagon and a pentagon ring. The calculations for electronic structures show that the magnetic moment of Sm is preserved for all the stable structures as tiny hybridization takes place between the orbitals of the Sm atom and those of their neighboring carbons. Because of the small energy gaps and the half occupation of the highest occupied molecular orbitals, all the stable $C60Sm$ isomers are inferred to be conductors.