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Frozen Density Embedding with External Orthogonality in Delocalized Covalent Systems
journal contribution
posted on 2015-07-14, 00:00 authored by Dhabih
V. Chulhai, Lasse JensenFrozen
density embedding (FDE) has become a popular subsystem density
functional theory (DFT) method for systems with weakly overlapping
charge densities. The failure of this method for strongly interacting
and covalent systems is due to the approximate kinetic energy density
functional (KEDF), although the need for approximate KEDFs may be
eliminated if each subsystem’s Kohn–Sham (KS) orbitals
are orthogonal to the other, termed external orthogonality (EO). We
present an implementation of EO into the FDE framework within the
Amsterdam density functional program package, using the level-shift
projection operator method. We generalize this method to remove the
need for orbital localization schemes and to include multiple subsystems,
and we show that the exact KS-DFT energies and densities may be reproduced
through iterative freeze-and-thaw cycles for a number of systems,
including a charge delocalized benzene molecule starting from atomic
subsystems. Finally, we examine the possibility of a truncated basis
for systems with and without charge delocalization, and found that
subsystems require a basis that allows them to correctly describe
the supermolecular delocalized orbitals.
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External OrthogonalityFDE frameworkcovalent systemscharge densitiesenergy densitycharge delocalizationDensity EmbeddingAmsterdam densitymethodEODFTsupermolecular delocalized orbitalsprogram packageKEDFcharge delocalized benzene moleculesubsystem densityKSDelocalized Covalent SystemsFrozen density embeddinglocalization schemes
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