Molecular electrostatic potential (ESP) represents the interaction energy between a unit charge at a given position and the molecule under study, with ignoring the effects of charge transfer and polarization. ESP distributed on molecular vdW surface is important as it exhibits the possible electrostatic interactions between the molecule under study and others. As shown in our previous report, ESP on the vdW surface of C 18 is distributed in a fairly low value range of -1.4 to 8.0 kcal/mol, indicating that C 18 is unlikely to generate significant electrostatic interactions with other molecules. Despite as can be seen from colors of vdW surface of OPP (Figure ), the local polarity of OPP is notably stronger than that of C 18 , the magnitude of the ESP over the inner side of its vdW surface (at most -17.8 kcal/mol, Figure ) is still unlikely large enough to cause a prominent electrostatic attraction with C 18 . The color scale is given in kcal/mol. The vdW surfaces of host and guest molecules in 2C 18 @OPP are concave-convex complementary and overlap with each other (Figure ), which clarifies the perfect matching of morphology and size of two moieties and suggests that there must exist a marked vdW interaction between them. The vdW potential of a molecule represents the vdW interaction energy between the molecule and a selected probe atom. It is an important supplement to the ESP in studying intermolecular interaction of a chemical system, especially when vdW interaction plays a dominant role while electrostatic interaction is less important, such as the case of C 18 ⋅⋅⋅OPP interaction.