It can be seen that the binding strength steadily increases with increasing the size of cyclocarbon until C34. This can be easily understood from the variation of g inter isosurfaces in Fig. , namely, the larger the cyclocarbon, the wider its prominent interaction region with C60 fullerene. The areas of the isosurfaces have a very good linear relationship with the binding energies (R 2 = 0.973) as shown in Fig. , indicating that the isosurface area is a useful descriptor for predicting the strength of - interactions without conducting energy calculations. It is found that C36 interacts less strongly with C60 fullerene than C34, mainly because the ring size of C36 is too large for fullerene to interact tightly with all its atoms simultaneously, as clearly illustrated by the IGMH map in Fig. .