Altered superatomic properties of U@C28 by the electron rearrangement via adatom defects

First-principles calculations show that when a carbon adatom has been introduced to the surface of U@C₂₈ superatom, the neutral U@C₂₉ has (cage)¹(adatom)¹ electronic state instead of (cage)² state in U@C₂₈. The valence orbitals of U atom keep fully occupied, while the origin of 32-electron principle is changed due to electron rearrangement via introducing the adatom. Furthermore, there exist two transition states when adatom slipping on the surface of U@C₂₈, indicating that it is a two-step process from [5: 5] to [6: 6] adsorption sites.