Quantum-Chemical Modeling of Two Er₃N@C₈₀ Isomers

Computations of the molecular parameters and relative populations are reported for the two isomers of Er₃N@C₈₀ experimentally known, i.e. produced by encapsulation into the isolated-pentagon-rule (IPR) C₈₀ cages with I _h and D _5h symmetries. The calculations are mostly based on the density-functional theory (DFT) treatments with the B3LYP functional. However, the inter-isomeric energetics is further refined with the B2PLYP method which places the D _5h endohedral higher in the potential energy by 18.8 kcal/mol. The isomeric populations are evaluated using the Gibbs energy in a broad temperature interval. The computations performed with the floating-encapsulate-model (FEM) treatment agree with the observation that Er₃N@I _h (7)-C₈₀ represents the major isomer. The calculations also suggest some similarity between Er₃N@C₈₀ and Lu₃N@C₈₀ so that Er₃N@C₈₀ could possibly also produce a useful nanowire, like recently found with Lu₃N@C₈₀ and its interesting electrical-conductivity and switching behavior.