Modified regional self-interaction corrected time-dependent density functional theory for core excited-state calculations.

A modified regional self-interaction correction (mRSIC) method is proposed for obtaining accurate core-excitation energies in time-dependent density functional theory (TDDFT) calculations. The mRSIC method is an improvement of the RSIC method (Tsuneda et al. J Comput Chem 2003, 24, 1592). It takes into account the energy contributions from 2s and higher atomic orbitals that the RSIC method neglects. Furthermore, mRSIC improves the poor description for the nuclear-electron cusp of Gaussian basis functions. The mRSIC method was combined with a long-range correction (LC) scheme, which has been proved to give accurate valence-, Rydberg-, and charge transfer (CT)-excitation energies. In so doing, it dramatically improved the accuracy of the calculated core-excitation energies and did not affect the already accurate values of valence-, Rydberg-, and CT-excitation energies produced by the LC functionals. These results mean that the combined scheme is accurate for all excitation energy forms.