Superatom states in an endohedral fullerene

Motivated by the recent discovery of superatom states in C$_{60}$[1], we studied the electronic structures of an endohedral fullerene, Sc$_{3}$N@C$_{80}$, adsorbed on copper surface by LT-STM experiment and DFT calculation. Both experimental and calculated results show that superatom states also exist in Sc$_{3}$N@C$_{80}$. Different from the C$_{60}$, the encapsulated cluster (Sc$_{3}$N-) in Sc$_{3}$N@C$_{80}$ distorts the nearly-spherical potential of the carbon cage, making the atom-like orbitals look asymmetric in the STM images. The adsorbed molecules exhibit various shapes of superatom orbitals due to the different orientation of the Sc$_{3}$N@C$_{80}$ on the surface. When two molecules form a dimer, however, the strong intermolecular hybridization overcomes the perturbation induced by the inside clusters, making all the dimers to have similar H$_{2 }$like molecular orbitals with clear bonding and anti-bonding characteristics. [1] Min Feng, Jin Zhao, Hrvoje Petek Science, 320,359, 2008.