2016 April 26, Jie Ma, Lin-Wang Wang, “Using Wannier functions to improve solid band gap predictions in density functional theory”, in Scientific Reports, volume 6, →DOI, article 24924, page 1:
There exists another approach to correct the DFT and its related Kohn-Sham Hamiltonian: the Koopmans’ theorem11–22. The original Koopmans’ theorem only states that in Hartree-Fock, the first ionization energy is equal to the highest occupied orbital energy if the wave function relaxations are ignored.
