First principles calculations of C70 fullerene nano-cage doped with transition

Abstract

Total energy calculations of the C70 fullerene nano-cage doped with transition metals, (TM¼Fe and Co<br><br>atoms), endohedrally, exohedrally, and substitutionally were performed using density functional<br><br>theory with the generalized gradient approximation along 18 different paths inside and outside of<br><br>the fullerene. The most stable structures were determined with full geometry optimization near the<br><br>minimum of the binding energy curves of all the examined paths. The results reveal that for all stable<br><br>structures, the Co atom has a larger binding energy than the Fe atom. It is also found that for all<br><br>complexes additional peaks contributed by TM-3d, 4s, and 4p states appear in the highest occupied<br><br>molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) gap of the host cluster.<br><br>The mid-gap states are mainly due to the hybridization between TM-3d, 4s, and 4p orbitals and the<br><br>cage p orbitals. The magnetic moment of endohedrally and exohedrally doped Fe and Co atoms in the<br><br>C70 fullerene are preserved to some extent due to the interaction between the TM and C atoms of the<br><br>cage, in contrast to the completely quenched magnetic moments of the Fe and Co atoms in the C69TM<br><br>complex. Furthermore, Mulliken charge population analysis shows that overall charge transfer occurs<br><br>from TM atom to the cage.