• adiabatic time-dependent DFT;
  • orbital relaxation;
  • self-interaction cancellation;
  • plastocyanin;
  • copper tetrachloride

Evaluation of the excitation energies in inline image and plastocyanin was carried out with three different density functional theory (DFT) methods: time-dependent DFT (TDDFT), ΔDFT, and Δself consistent field (SCF)-DFT. Use was made of two local (local density approximation and BP86), two hybrid (B3LYP and PBE0), and one long-range corrected (LC-BP86) functionals to probe the effect of the exact exchange on the excitation energies. Some well-known deficiencies observed in TDDFT were explained on the basis of lacking orbital relaxation and two-electron terms not considered in adiabatic TDDFT. Δself consistent field (SCF)-DFT reproduces well the position of the charge-transfer excitations and yields results in best agreement with experiment regardless of the system or functional used. We conclude that the orbital relaxation and proper account of higher-order terms neglected in adiabatic TDDFT are of great importance for the simulation of excitation spectra. © 2014 Wiley Periodicals, Inc.