Computed structure and energetics of La@C ₆₀

Computations are carried out using density functional theory for the endohedral system La@C ₆₀, i.e., the very first metallofullerene observed in gas phase (although not yet isolated in a solid form). The computations offer data on the molecular and electronic structure of the species. In particular, it is shown that the encapsulated atom is not located in the cage center, but is shifted toward the wall. There is a substantial charge transfer from the metal to the cage, at some levels of theory amounting roughly to three electrons. It is shown that there is a relatively large energy stabilization upon encapsulation. However, the entropy term also influences the association equilibrium significantly, so that the standard Gibbs-energy change depends strongly on temperature. The reasons why La@C ₆₀ could not be isolated yet are briefly discussed, as well as a possible relationship to superconductivity.