Local hybrid alternatives to the orbital density approximation reduce the orbital dependence of self-interaction...

This work presents local hybrid alternatives to the orbital density approximation employed in self-interaction corrected density functional theory (SIC-DFT) and extended for use in DFT-corrected correlated wavefunction approaches (CAS-DFT). When combined with standard approximate density functionals, the orbital density approximation leaves SIC-DFT energies strongly dependent on unitary transforms among occupied orbitals and leaves CAS-DFT energies overbound. The alternatives presented here reduce both errors. The orbital density approximation and the local hybrid alternatives are shown to approximate an underlying nondiagonal exchange-correlation hole. A preliminary extension is presented to active-virtual correlation. These results motivate exploration of local hybrid concepts in SIC-DFT and CAS-DFT.