Journal Article

PreJuSER-9022

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Efficient implementation of the GW approximation within the all-electron FLAPW method

Friedrich, C.FZJ* ; Blügel, S.FZJ* ; Schindlmayr, A.

2010
APS College Park, Md.

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Please use a persistent id in citations: http://hdl.handle.net/2128/10998  doi:10.1103/PhysRevB.81.125102

Abstract: We present an implementation of the GW approximation for the electronic self-energy within the full-potential linearized augmented-plane-wave (FLAPW) method. The algorithm uses an all-electron mixed product basis for the representation of response matrices and related quantities. This basis is derived from the FLAPW basis and is exact for wave-function products. The correlation part of the self-energy is calculated on the imaginary-frequency axis with a subsequent analytic continuation to the real axis. As an alternative we can perform the frequency convolution of the Green function G and the dynamically screened Coulomb interaction W explicitly by a contour integration. The singularity of the bare and screened interaction potentials gives rise to a numerically important self-energy contribution, which we treat analytically to achieve good convergence with respect to the k-point sampling. As numerical realizations of the GW approximation typically suffer from the high computational expense required for the evaluation of the nonlocal and frequency-dependent self-energy, we demonstrate how the algorithm can be made very efficient by exploiting spatial and time-reversal symmetry as well as by applying an optimization of the mixed product basis that retains only the numerically important contributions of the electron-electron interaction. This optimization step reduces the basis size without compromising the accuracy and accelerates the code considerably. Furthermore, we demonstrate that one can employ an extrapolar approximation for high-lying states to reduce the number of empty states that must be taken into account explicitly in the construction of the polarization function and the self-energy. We show convergence tests, CPU timings, and results for prototype semiconductors and insulators as well as ferromagnetic nickel.

Keyword(s): J

Note: The authors acknowledge valuable discussions with Markus Betzinger, Andreas Gierlich, Gustav Bihlmayer, Takao Kotani, Mark van Schilfgaarde, and Tatsuya Shishidou as well as financial support from the Deutsche Forschungsgemeinschaft through the Priority Program 1145.

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Contributing Institute(s):

1. Quanten-Theorie der Materialien (IFF-1)
2. Quanten-Theorie der Materialien (IAS-1)
3. Jülich-Aachen Research Alliance - Fundamentals of Future Information Technology (JARA-FIT)
4. Jülich Aachen Research Alliance - High-Performance Computing (JARA-HPC)

Research Program(s):

1. Grundlagen für zukünftige Informationstechnologien (P42)

Appears in the scientific report 2010

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