Schedule Nov 21, 2002
All-electron GWA based on the PAW method: application to the electronic structure of insulating materials
Mebarek Alouani, IPCMS
http://www-ipcms.u-strasbg.fr/gemm/people/alouani/
In this talk I will discuss the implementation of the GW approximation (GWA) based on an all-electron Projector-Augmented-Wave (PAW) method for computing the quasiparticle properties of materials. Within this approach, the self-energy is a product of the one-particle Greenís function G and the dynamically screened interaction W computed using either the random phase approximation (RPA) or the so-called plasmon-pole model (PPM). Starting from the calculated local density approximation (LDA) ground state, the LDA eigenvalues are corrected by treating the difference between the self-energy and the exchange-correlation potential as a perturbation. The calculated quasiparticle energies obtained by means of this procedure are, generally, in good agreement with experiment. It is surprizing, however, that the quasiparticle energies of semiconductors are found to be neither sensitive to the scheme used for decoupling the core and valence electrons nor to the different type of PPMs used to produce the dynamically screened interaction W. If times permits, I will discuss how the quasiparticle energies are then used to compute the macroscopic dielectric function including both the local-field and the excitonic (electron-hole interaction) effects. The standard procedure for including these effects in the calculation of the dielectric function consists in solving the so-called Bethe-Salpeter equation. This approach has been applied to different semiconductors and insulators, and it has been shown that the inclusion of electron-hole attraction is necessary for a detailed comparison of the theoretical and experimental optical spectra.

Work done in collaboration with S. Lebègue and B. Arnaud

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