Structural properties of endohedral C60 fullerens studied by DFT

The bonding of alkali-earth, transition metal and lanthanide atoms in C-60 is studied using density functional theory. In agreement with previous studies [1-3], tile bonding is found to be mostly ionic, but a significant hybridisation between the metal d orbitals and carbon p orbitals is also encountered. For all metal atoms we find a similar energetic site ordering, where adsorption in the proximity of the hexagonal rings is most favourable. The energy differences between different adsorption sites however varies strongly with the metal atom. For metal atoms without d electrons, such as Ca, the potential energy surface is fairly flat, which should result in a significantly higher mobility.