Analysis of self-interaction correction for describing core excited states

Core-excitation energies are calculated by the self-interaction-corrected time-dependent density functional theory (SIC-TDDFT) and SIC-delta-self- consistent field (SIC-ΔSCF) methods. For carbon monoxide, SIC-TDDFT severely overestimates core-excitation energies, while the SIC-ΔSCF method using Kohn-Sham density functional theory (KS-DFT) slightly overestimates. These behaviors are attributed to the fact that the self-interaction errors in the total and orbital energies considerably differ. We evaluate the difference of the self-interaction errors for the Slater exchange functional.