Calculated isomeric populations of Er@C₈₂

Relative populations of the four energy-lowest IPR (isolated-pentagon-rule) isomers of Er@C₈₂ under the high-temperature synthetic conditions are computed using the Gibbs energy based on characteristics from the density functional theory calculations (B3LYP/6-31+G*∼SDD energetics, B3LYP/6-31G*∼SDD entropy). Two leading isomers are predicted - Er@ (Formula presented.) -C₈₂ and Er@ (Formula presented.) -C₈₂. The calculated equilibrium isomeric relative populations agree with available observations. As Er@C₈₂ is one of the metallofullerenes recently used as dopants for improvement of efficiency and stability of perovskite solar cells, the calculations should help in finding rules for further selections of fullerene endohedrals for such new applications in photovoltaics.