Sc 3 N@C 80 : Computations on the Two‐Isomer Equilibrium at High Temperatures

Reported herein are computations on the relative concentrations of the two experimentally known isomers of Sc 3 N@C 80 , that is, those produced by encapsulation of Sc 3 N in two particular C 80 cages that obey the isolated‐pentagon rule, namely, with I h and D 5 h symmetries. The calculations are based on density functional methods and have been carried out using the Gibbs energy over a broad temperature interval. It has been computed that, if a relatively free motion of the encapsulate inside the cages is allowed, the observed populations of 10 and 17 % for the D 5 h Sc 3 N@C 80 species are reached at temperatures of 2100 and 2450 K, respectively. The inclusion of the entropy term is essential as, if it is neglected, the D 5 h Sc 3 N@C 80 population at a temperature of 2100 K would be a mere 1 %, owing to the relatively large interisomeric separation potential energy of 19 kcal mol −1 .