Precise all-electron dynamical response functions: Application to COHSEX and the RPA correlation energy

Markus Betzinger, Christoph Friedrich, Andreas Görling, and Stefan Blügel
Phys. Rev. B 92, 245101 – Published 1 December 2015

Abstract

We present a methodology to calculate frequency and momentum dependent all-electron response functions determined within Kohn-Sham density functional theory. It overcomes the main obstacle in calculating response functions in practice, which is the slow convergence with respect to the number of unoccupied states and the basis-set size. In this approach, the usual sum-over-states expression of perturbation theory is complemented by the response of the orbital basis functions, explicitly constructed by radial integrations of frequency-dependent Sternheimer equations. To an essential extent an infinite number of unoccupied states are included in this way. Furthermore, the response of the core electrons is treated virtually exactly, which is out of reach otherwise. The method is an extension of the recently introduced incomplete-basis-set correction (IBC) [Betzinger et al., Phys. Rev. B 85, 245124 (2012); Phys. Rev. B 88, 075130 (2013)] to the frequency and momentum domain. We have implemented the generalized IBC within the all-electron full-potential linearized augmented-plane-wave method and demonstrate for rocksalt BaO the improved convergence of the dynamical Kohn-Sham polarizability. We apply this technique to compute (a) quasiparticle energies employing the COHSEX approximation for the self-energy of many-body perturbation theory and (b) all-electron RPA correlation energies. It is shown that the favorable convergence of the polarizability is passed over to the COHSEX and RPA calculation.

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  • Received 6 August 2015

DOI:https://doi.org/10.1103/PhysRevB.92.245101

©2015 American Physical Society

Authors & Affiliations

Markus Betzinger1,*, Christoph Friedrich1, Andreas Görling2, and Stefan Blügel1

  • 1Peter-Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, D-52425 Jülich, Germany
  • 2Lehrstuhl für Theoretische Chemie, Universität Erlangen-Nürnberg, Egerlandstr. 3, D-91058 Erlangen, Germany

  • *m.betzinger@fz-juelich.de

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Vol. 92, Iss. 24 — 15 December 2015

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