Dimetallofullerene M2@C100 or carbide cluster fullerene M2C2@C98 (M = La, Y, and Sc): which ones are more stable?

Abstract

The geometric and thermodynamic stability of the M₂C₁₀₀ (M = La, Y, and Sc) series was systematically investigated using density functional theory calculations on the level of B3LYP/6-31G(d) ∼ Lanl2dz. In all the cases, M₂@D₅(285913)-C₁₀₀ isomers are the lowest-energy species. However, carbide endohedral fullerenes M₂C₂@C₁(230933)-C₉₈ present excellent thermodynamic stabilities, except for those with La metal. The main product in electric arc experiments at temperatures lower than 3500 K for La₂C₁₀₀ should be La₂@D₅(285913)-C₁₀₀, which was successfully synthesized previously; for Y and Sc, the predicted main products in these experiments should be M₂C₂@C₁(230933)-C₉₈. Further analysis of the geometric structures of the M₂C₁₀₀ series showed that the dimetallofullerenes M₂@C₁₀₀ have greater effects on the shapes of cages than M₂C₂@C₉₈. These results provide some valuable guidance for the synthesis and characterization of large endohedral fullerenes including La, Y or Sc.