# Regensburg 2016 – wissenschaftliches Programm

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# MM: Fachverband Metall- und Materialphysik

## MM 15: Poster session I

### MM 15.17: Poster

### Montag, 7. März 2016, 18:00–20:00, Poster B3

**A fast Fermi orbital based self-interaction correction:
A preconditioned Conjugate Gradient algorithm** — •Lenz Fiedler, Charlotte Vogelbusch, Torsten Hahn, and Jens Kortus — TU Freiberg, Institute for Theoretical Physics, Germany

In order to optimize methodical errors of density functional theory (DFT), a sufficient self-interaction correction (SIC) is needed.
A possible approach is realized by the construction of localized orbitals such as Fermi orbitals, which can be obtained from Kohn-Sham orbitals.
A full theoretical description of such a Fermi orbital based SIC is given by Pederson [1,2] drawing on previous results by Perdew and Zunger [3]. The implementation of this approach in a DFT code causes some numerical problems, due to the slow convergence in the optimization of the Fermi orbital positions.

Therefore we present an implementation of a conjugate gradient algorithm that is likely to improve the convergence of the calculation and therefore decreases the computational time. This is done by using a preconditioner which is composed of the diagonal elements of the Hessian of the energy function. These diagonal elements have been implemented both analytically and numerically. We show benchmarks against each other for a set of small molecules.

M. R. Pederson et al., J. Chem. Phys., vol. 140, 121103 (2014)

M. R. Pederson, J. Chem. Phys., vol. 142, 064112 (2015)

J. Perdew, A. Zunger, Phys. Rev. B 23, 5048 (1981)