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Issue 31, 2016
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No need for external orthogonality in subsystem density-functional theory

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Abstract

Recent reports on the necessity of using externally orthogonal orbitals in subsystem density-functional theory (SDFT) [Annu. Rep. Comput. Chem., 8, 2012, 53; J. Phys. Chem. A, 118, 2014, 9182] are re-investigated. We show that in the basis-set limit, supermolecular Kohn–Sham-DFT (KS-DFT) densities can exactly be represented as a sum of subsystem densities, even if the subsystem orbitals are not externally orthogonal. This is illustrated using both an analytical example and in basis-set free numerical calculations for an atomic test case. We further show that even with finite basis sets, SDFT calculations using accurate reconstructed potentials can closely approach the supermolecular KS-DFT density, and that the deviations between SDFT and KS-DFT decrease as the basis-set limit is approached. Our results demonstrate that formally, there is no need to enforce external orthogonality in SDFT, even though this might be a useful strategy when developing projection-based DFT embedding schemes.

Graphical abstract: No need for external orthogonality in subsystem density-functional theory

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Publication details

The article was received on 15 Jan 2016, accepted on 08 Feb 2016 and first published on 15 Feb 2016


Article type: Paper
DOI: 10.1039/C6CP00332J
Phys. Chem. Chem. Phys., 2016,18, 21001-21009
  • Open access: Creative Commons BY license
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    No need for external orthogonality in subsystem density-functional theory

    J. P. Unsleber, J. Neugebauer and C. R. Jacob, Phys. Chem. Chem. Phys., 2016, 18, 21001
    DOI: 10.1039/C6CP00332J

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