Regensburg 2013 – scientific programme

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O: Fachverband Oberflächenphysik

O 17: Focussed Session: Frontiers of Electronic Structure Theory II (jointly with HL and TT)

O 17.12: Talk

Monday, March 11, 2013, 18:45–19:00, H36

Acceleration of the response function convergence using the effective energy techniques within the ultrasoft pseudopotential and PAW methods — •Jiří Klimeš and Georg Kresse — Faculty of Physics, University of Vienna, A-1090 Vienna, Austria

Calculations of quasiparticle spectra based on the GW approximation or evaluation of total energies using the RPA method are of a wide interest in the computational materials community. However, their applicability is to a large extent limited by the cost of evaluating the response function or the selfenergy where a large number of unoccupied bands needs to be included. A promising way to speed-up the convergence is to use the resolution of identity and replace the sum over an infinite number of unoccupied states by an effective correction [1,2]. However, the available schemes have been only formulated for norm-conserving pseudopotentials and when applied directly within the ultrasoft pseudopotentials (USPPs) or the PAW method they introduce an error since the correction term doesn’t vanish when the number of included bands is increased. Here we present an implementation of the schemes within the formalism of USPPs or the PAW method which gives the proper behaviour of the correction term. We also show how the convergence of the scheme given in [2] can be further improved and discuss the efficiency of the methods for RPA total energy calculations.

[1] F. Bruneval and X. Gonze, PRB 78, 085125 (2008)

[2] J. A. Berger, L. Reining, and F. Sottile, PRB 82, 041103(R) (2010); PRB 85, 085126 (2012)