# Dresden 2009 – wissenschaftliches Programm

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# O: Fachverband Oberflächenphysik

## O 21: Methods: Electronic structure theory I

### O 21.6: Vortrag

### Dienstag, 24. März 2009, 11:45–12:00, SCH A316

**Massive parallelization of the KKR Green-function method for large scale ab-initio calculations** — •Alexander Thiess, Rudolf Zeller, and Stefan Blügel — Institut für Festkörperforschung and Institute for Advanced Simulation, Forschungszentrum Jülich, 52545 Jülich, Germany

Recent experimental progress in the analysis of oxide interfaces reveals
the importance of complex defects arising from local disorder or
oxygen vacancies on transport and magnetic properties of the system [1].
For a theoretical treatment by density-functional calculations large
unit cells containing thousands of atoms are unavoidable.
As existing density-functional methods are usually restricted to a few hundreds of atoms in the unit cell,
we have developed an algorithm based on the KKR Green-function method capable of treating geometries consisting of several thousands of inequivalent
atoms. We combine the advantages of the screened KKR formalism and an iterative solution of the Dyson equation [2]
with the new generation of massively parallelized computers to obtain a parallelization over the number of atoms in the unit cell. Calculations of test systems with up to 4096 atoms
in the unit cell show that our algorithm scales efficiently on the Jülich
BlueGene computer JUGENE [3] for several thousands of processores.

[1] A. Ohtomo, H. Y. Hwang, Nature **427**, 423 (2004)

[2] R. Zeller, J. Phys.: Condens. Matter **20**, 294215 (2008)

[3] http://www.fz-juelich.de/jsc/jugene