Identifying Tm@C82 isomers with density functional theory calculations.

Density functional theory calculations have been performed to study the geometrical and electronic properties of endohedral metallofullerene Tm@C(82) isomers. Three energetically favorable isomers (with C(s), C(2) and C(2v) symmetry, respectively) are identified which are consistent with the nuclear magnetic resonance (NMR) observations. The simulated ultraviolet photoelectron spectra (UPS) based on the three structures agree well with the measurements. Particularly, the parent cage of the experimentally observed Tm@C(82) isomer with C(s) symmetry is newly assigned, which matches the experiments better than early assignments. In addition, strong interaction between an endohedral Tm atom and the C(82) cage is discussed and is thought to be responsible for the dramatic change in the relative stability of C(82) isomers when Tm is encapsulated.