The equilibrium geometry of A@C60: A test case for conventional density functional theory

Potential energy surfaces (PESs) along the reaction pathway towards the center of CC bond between two six membered rings for ten different endohedral fullerenes A@C60 (A = H, C, O, S, N, P, He, Ne, Ar, Kr) have been studied by density functional theory (DFT) and Hartree–Fock (HF) method. The results show that no suitable method can consistently describe the interaction between atom A and carbon cage. The dispersion corrected DFT methods fail to describe the equilibrium geometry and PES of the complexes with light atoms. Nevertheless, the inclusion of the dispersion stabilizes the system as reflected by interaction energies (IEs) between atom A and C60.