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HL: Halbleiterphysik
HL 8: III-V Halbleiter I
HL 8.2: Vortrag
Freitag, 4. März 2005, 12:00–12:15, TU P-N202
Generalised Wannier Functions: An accurate and efficient way to construct ab-initio tight-binding orbitals — •Matthias Wahn1,2 and Jörg Neugebauer1,2 — 1Fritz-Haber-Institut, Faradayweg 4-6, 14195 Berlin-Dahlem — 2Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straße 1, 40237 Düsseldorf
The tight-binding approximation (TB) provides an efficient and physically transparent basis set. Commonly, the corresponding orbitals and matrix elements are constructed starting from a minimum number of free or confined atomic orbitals. A problem with this approach is that it provides only an approximate basis set for which the completeness is hard to control. Generalized Wannier functions (GWF) [1] provide a minimum basis set while conserving the completeness of the original basis set and provide thus an interesting option. We have therefore implemented the generation of GWF in our plane wave pseudopotential code SFHIngX and checked the efficiency (number of non-vanishing matrix elements) and accuracy (compared to the original band structure) for various III-V semiconductors (GaAs, GaN, InN) and different exchange correlation functionals (LDA, EXX). Based on these results we show that the commonly applied localization criterion (spread function) is not sufficient but that a careful choice of the GWF allows a dramatic improvement of the efficiency.
Nicola Marzari and David Vanderbilt, Phys. Rev. B 56, 12847 (1997).