DFT results against experimental data for electronic properties of C₆₀ and C₇₀ fullerene derivatives

Some electronic properties of different C₆₀ and C₇₀ derivatives were evaluated using 20 density functionals (the B3LYP, BHANDH, PBE0, HSE06, CAM-B3LYP, ωB97X-D, BMK, PBEPBE, M06-L, M06, M06-2X, M06-HF, PW91PW91, BLYP, B97D, HCT407, τ-HCTH, τ-HCTHhyb, TPSS, and LSDA), and some of the results were compared with the available experimental data. Unlike in Hartree-Fock (HF) method, the orbital relaxation is not the origin of the violation of DFT from the Koopmans' theorem. For most of functionals, the HOMO-LUMO gap (E_g) is more sensitive to the functional compared to the optical gap. The functionals with a large %HF exchange significantly overestimate the E_g, and are not suggested for electronic calculations. All non-hybrid functionals underestimate the value of |HOMO| in comparison to the experimental ionization potential (IP_e). In the hybrid functionals, the HOMO level becomes more stable by increasing %HF exchange and even in some functionals with a large %HF, |HOMO| overestimates the IP_e.