shows the NCI map of the complexes formed by Cs + and different buckybowls. It can be seen that as the buckybowl changes from the fully open P1 to the fully closed C60 fullerene, the complexation energy gradually shifts from a relatively negative value towards zero and ultimately becomes significantly positive. Correspondingly, under the small color scale range (-0.01 to 0.01 a.u.), the RDG isosurface changes from light blue to green, and then to red, intuitively reflecting that the steric hindrance becomes stronger and stronger, causing the interaction between Cs + and the buckybowl to shift from attractive to repulsive. This example demonstrates that the NCI visualization analysis can effectively exhibit the strength and characteristics of the interaction of interest. Reprinted with permission from Ref. . Copyright 2015 Elsevier.