Berlin 2008 – wissenschaftliches Programm

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SYEC: Symposium Exact-exchange and hybrid functionals meet quasiparticle energy calculations

SYEC 3: Exact-exchange and hybrid functionals meet quasiparticle energy calculations III - Poster (joined by SYMS posters)

SYEC 3.1: Poster

Donnerstag, 28. Februar 2008, 18:30–19:30, Poster F

Implementation of exact exchange in a real-space DFT code using the projector augmented wave method — •Carsten Rostgaard and Jens Jørgen Mortensen — Center for Atomic-scale Materials Design, Technical University of Denmark, Denmark

The projector augmented wave (PAW) method for density-functional theory (DFT) calculations, offers a formally well defined linear transformation from the sharply featured all-electron wave function to the smooth pseudo wave function, thus enabling a computationally efficient approach to solving the Kohn-Sham equations, while retaining the accuracy of a full potential (frozen core) calculation.

As DFT calculations with orbital dependent exchange-correlation functionals probe the core region of the wave function, the PAW scheme is ideally suited for such functionals. For exact exchange calculations in PAW, one needs to determine the action of the non-local Fock operator on the smooth pseudo wavefunctions. The Fock operator can then be applied directly, as is done in most hybrid functionals, of it can be `localized' (i.e. made multiplicative) by some appropriate scheme, like OEP, LHF, KLI, etc.

We have implemented the Fock operator in the real-space PAW-DFT code gpaw, and a benchmark test of the atomization energies and HOMO-LUMO gaps of a number of small molecules has been performed, and compared to calculations done in VASP and Gaussian, using the PBE0 hybrid functional. We find that the effect of the valence-core exchange interaction, available in the PAW framework, can be substantial.