, and 60 (C ) E stand for the electronic energies calculated for the complex of two cyclocarbons, the first cyclocarbon, the second cyclocarbon, the C60@2Cn trimer, and the C60 fullerene, respectively. All energies were evaluated based (b) that the interaction strength between the two cyclocarbons increases steadily and slowly as the ring size varies from C18 to C30. The interaction between the two C34 rings in C60@2C34 is quite significant (-17.3 kcal/mol), which is in line with the observation in Fig. that only two C34 can form a complete - interaction with each other, while this interaction in other trimer can only occur within a very limited contact area.