With the discovery of two minimum structures of C60@C18 dimer in mind, the possibility of relative rotation between C60 fullerene and cyclocarbons is also worth exploring. At the same computational level as geometry optimization, we located the transition state between C60@C18 dimers of different configurations, which has a unique imaginary frequency of 9.8i cm -1 . The corresponding normal coordinate of the transition state is plotted as Fig. , which clearly demonstrates the relative sliding tendency of C60 relative to the C18 and characterizes the interconversion between the two configurations. The forward and reverse potential barriers calculated at the B97M-V/def2-QZVPP level are extremely low of 0.90 and 0.04 kcal/mol, respectively, indicating that configuration conversion can occur very frequently. For complexes formed by C60 fullerene and other cyclocarbons, due to their π-π interaction characteristics similar to that of C60@C18, relative motion between the two molecules must also be very easy. After a C60 fullerene and a cyclocarbon form a dimer, another cyclocarbon or fullerene can be further combined with it to form a trimer. In the following two sections, we investigated the possible geometric structures, binding strength, and interaction nature of trimers composed of C60 fullerene and cyclocarbon with 1:2 and 2:1 manners.