Symmetry-adapted perturbation theory (SAPT) analysis is well suited to quantitatively understand the physical components of intermolecular interactions, and has been employed by us to gain insight into the non-covalent adsorption of C 18 . Although the calculated E int of -30.0 kcal/mol at SAPT0/jun-cc-pVDZ level is obviously different from the more accurate ωB97M-V/def2-QZVPP results mentioned above (-20.3 kcal/mol), the relative contribution of its components is still helpful in understanding the nature of the intermolecular interactions. The energy decomposition analysis showed that most of the attraction between C 18 and OPP comes from the dispersion effect (-42.8 kcal/mol), while the electrostatics interaction (-13.3 kcal/mol) is less significant, and the induction effect from orbital interaction (-3.1 kcal/mol) is almost negligible. This finding is in excellent agreement with our above inferences from the ESP distribution on the vdW surfaces, molecular vdW potential, and Mayer bond order.