Nov 21, 2002
All-electron GWA based on the PAW method: application to the electronic structure of insulating materials
Mebarek Alouani, IPCMS
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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