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SYAI: Symposium Ab-Initio Approaches to Excitations in Condensed Matter

SYAI 1: Invited Talks

SYAI 1.2: Hauptvortrag

Donnerstag, 26. März 2009, 15:30–16:00, SCH 251

Quasiparticle energy calculations in a new light: from defects in semiconductors to the f-electron challenge — •Patrick Rinke — University of California at Santa Babara, CA 93106, USA

Focussing on spectroscopic aspects of semiconductors and insulators we will illustrate how quasiparticle energy calculations in the G₀W₀ approximation can be successfully combined with recent developments in density functional theory (DFT) to meet the challenges in the theoretical description of the electronic properties of these materials. For defects in semiconductors we present a new formalism that expresses their formation energy as successive charging of a configuration with unoccupied defects states. We demonstrate for the example of the self-interstitial in silicon that G₀W₀ overcomes the self-interaction and band-gap problem of the local-density approximation (LDA) to DFT and increases the formation energy of the neutral configuration by ∼1.1 eV. For group-III-nitrides and lanthanide oxides it proves necessary to remove or reduce the self-interaction already at the ground state level, which we achieve by using the exact-exchange optimized effective potential approach (OEPx) and a Hubbard-U correction to the LDA, respectively. We demonstrate that the band parameters for group-III-nitrides derived from G₀W₀@OEPx are in very good agreement with the available experimental data and provide reliable predictions for all parameters which have not been determined experimentally so far. The good agreement of the G₀W₀@LDA+U results with available experimental data for the lanthanide oxide series leads us to challenge the conventional view that regards these materials as strongly correlated.