Single Hamiltonian for self-interaction corrected DFT with Fermi-Lowdin orbitals

The self-interaction error in density functional approximation arises from the incomplete cancellation of self-Coulomb by self-exchange. The self-interaction correction proposed by Perdew and Zunger corrects for this error through an orbital by orbital scheme. The resulting SI corrected potential for the electrons becomes orbital dependent. The original SI corrected energy was not unitarily invariant with respect to orbital transformations. The energy minimization requires finding the set of orbitals that minimizes the total energy. Recent development of Fermi-Lowdin orbital based self-interaction correction scheme is a step forward in that energy is unitarily invariant under orbital transformation to localized Fermi Lowdin orbitals. We show that within the Fermi-Lowdin orbital based self-interaction correction scheme it is also possible to derive a single Kohn-Sham multiplicative Hamiltonian for all orbitals which decreases the computational complexity. Implementation of this method is discussed and the results show that the energy is slightly lower and required time is significantly less than other approximate methods for obtaining the canonical orbitals.