Massively parallel density functional calculations for thousands of atoms: KKRnano

Thiess, A.; Zeller, R.; Blügel, S.; Bolten, M.; Dederichs, P. H.

doi:10.1103/PhysRevB.85.235103

Journal Article

PreJuSER-21269

Massively parallel density functional calculations for thousands of atoms: KKRnano

Thiess, A.FZJ* ; Zeller, R.FZJ* ; Bolten, M. ; Dederichs, P. H.FZJ* ; Blügel, S.FZJ*

2012
APS College Park, Md.

Physical review / B 85(23), 235103 (2012) [10.1103/PhysRevB.85.235103]

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Please use a persistent id in citations: http://hdl.handle.net/2128/10861 doi:10.1103/PhysRevB.85.235103

Abstract: Applications of existing precise electronic-structure methods based on density functional theory are typically limited to the treatment of about 1000 inequivalent atoms, which leaves unresolved many open questions in material science, e. g., on complex defects, interfaces, dislocations, and nanostructures. KKRnano is a new massively parallel linear scaling all-electron density functional algorithm in the framework of the Korringa-Kohn-Rostoker (KKR) Green's-function method. We conceptualized, developed, and optimized KKRnano for large-scale applications of many thousands of atoms without compromising on the precision of a full-potential all-electron method, i.e., it is a method without any shape approximation of the charge density or potential. A key element of the new method is the iterative solution of the sparse linear Dyson equation, which we parallelized atom by atom, across energy points in the complex plane and for each spin degree of freedom using the message passing interface standard, followed by a lower-level OpenMP parallelization. This hybrid four-level parallelization allows for an efficient use of up to 100 000 processors on the latest generation of supercomputers. The iterative solution of the Dyson equation is significantly accelerated, employing preconditioning techniques making use of coarse-graining principles expressed in a block-circulant preconditioner. In this paper, we will describe the important elements of this new algorithm, focusing on the parallelization and preconditioning and showing scaling results for NiPd alloys up to 8192 atoms and 65 536 processors. At the end, we present an order-N algorithm for large-scale simulations of metallic systems, making use of the nearsighted principle of the KKR Green's-function approach by introducing a truncation of the electron scattering to a local cluster of atoms, the size of which is determined by the requested accuracy. By exploiting this algorithm, we show linear scaling calculations of more than 16 000 NiPd atoms.

Keyword(s): J

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Physics, Condensed Matter

Note: We like to thank W. Lambrecht and P. Mavropoulos for fruitful discussions. Financial support of the DAAD and both computational resources as well as technical support of the Julich Supercomputing Center are gratefully acknowledged. This work benefited from discussions within the SFB 917 Nanoswitches.

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Appears in the scientific report 2012

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Medline