Generalized Kohn-Sham equations with accurate total energy and single-particle eigenvalue spectrum.

We propose a new generalized Kohn-Sham or constrained hybrid method, where the exchange potential is the (equally weighted) average of the nonlocal Fock-exchange term and the self-interaction-corrected exchange potential, as obtained from our constrained minimization method of semi-local approximations. The new method gives an accurate single-particle eigenvalue spectrum with an average deviation between (the negative of) the valence orbital eigenvalues and the experimental ionization potentials of about 0.5 eV, while the deviation of core orbitals is within 2 eV. The improvement in the eigenvalue spectrum is achieved with a minimal increase in the total energy.