Dresden 2014 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 99: Electronic structure theory

HL 99.2: Talk

Thursday, April 3, 2014, 15:15–15:30, POT 151

Predictive GW calculations with pseudopotentials and plane-waves — •Jiri Klimes and Georg Kresse — Faculty of Physics, University of Vienna, Sensengasse 8/12, A-1090 Wien, Austria

The GW approximation is the standard approach to obtain quasi-particle (QP) energies in solid state physics. Despite its wide use, the agreement between values obtained by different implementations is often unsatisfactory, even for the simplest case of G₀W₀@LDA. This is often attributed to the use of pseudopotentials or to the limited size of local basis sets in all-electron codes. Moreover, little attention is usually paid to obtain results that are converged with respect to the size of the basis sets for orbitals and for the response function. Here we derive an analytic formula for the contribution of unoccupied states with high kinetic energies to the QP corrections. This clearly shows the necessity to converge with the number and basis set size for unoccupied states as well as with the basis set size for the response function. It also points to a problem in the current projector-augmented-wave (PAW) GW calculations that originates from the incompleteness of the on-site basis set of partial waves. We show that this issue can be avoided by using norm-conserving PAW partial-waves in the GW calculations. Our results are then in a very good agreement with the values obtained using all-electron FLAPW+lo method, even for the problematic case of ZnO [1].

[1] C. Friedrich, M. C. Müller, and S. Blügel, PRB 83, 081101(R) (2011); 84, 039906 (2011).