It is worth mentioning that we have reported an interaction energy of -9.2 kcal/mol between the monomers in the π-π stacking dimer formed by two C18, while the binding energy of C60@C18 obtained in this work is -14.4 kcal/mol. This indicates the interaction strength between C18 and C60 fullerene is significantly stronger than that between two C18. In addition, the binding energy of C60@C18 is also significantly greater than that between two C60 fullerenes, estimated to be -8.3 kcal/mol by the very accurate DLPNO-CEPA/1 method with complete basis set extrapolation. Therefore, we can conclude that the cyclocarbon systems have an inherent strong affinity with C60 fullerene.