A stable unconventional structure of Sc2@C66 found by density functional calculations

To provide theoretical insight into the cage structure and metal position of Sc2@C66, density functional calculations are carried out. The endohedral structure determined by the maximum-entropy-method (MEM)/Rietveld analysis of synchrotron X-ray powder diffraction data does not correspond to an energy minimum. Instead, a much more stable C2v structure is found, which satisfies the observed 13C NMR spectrum. Two Sc atoms are highly stabilized in the non-classical C2v fullerene cage containing two pairs of threefold fused pentagons.