Efforts at improving density-functional approximations, including recent data-driven or genomic approaches, have trended toward extracting parameterizations of the energy functional so that it is able to reproduce, in a least-square sense, large databases of molecular properties. As functionals include more and more density derivatives, it will become desireable to minimize the total number of parameters through construction of functional forms that are constrained to obey known properties or behaviors of the exact functional. The self-interaction correction (SIC), originally due to Perdew and Zunger, was suggested as a means for exactly reproducing the asymptotic behavior of the effective potential and ensuring that any self-interaction corrected functional is correct in the single-electron limit. However the explicit orbital dependence, or alternatively unitary non-invariance, for the functional associated with this formulation leads to a large increase in computational costs due to the need to solve the localization equations for SIC[1]. In recent work a size-extensive unitarily invariant reformulation of the self-interaction correction has been introduced by constructing the SIC functional in terms of Lowden-orthonormalized Fermi orbitals[2]. Such orbitals are explicitly dependent on the single-particle density matrix but depend parametrically on a set of quasi-classical electronic positions that are variationally optimized to minimize the SIC potential. An overview of this method will be provided with attention to the calculation of the energy gradients associated with the quasi-classical electronic positions. Possible advantages for use of this method for calculations on materials containing simple gas-phase molecules, molecules with open metal centers and molecular magnets will be discussed. At the level of local density-functional theory cohesive energies for systems containing pi-bonds are significantly improved. Occupied orbital eigenvalues are corrected significantly and more close match experimental ionization potentials of the system. The ability to achieve DFT-based scaling within this “Fermi-Orbital SIC” will be discussed. [1]M.R. Pederson, R.A. Heaton and C.C. Lin, J. Chem. Phys. 80, 1972 (1984). [2]M. R Pederson, A. Ruzsinszky and J. P. Perdew, J. Chem. Phys. 140 121103 (2014).

Self-interaction correction to density-functional approximations with unitary invariance

249th National Meeting (2015)

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