Issue 31, 2016

No need for external orthogonality in subsystem density-functional theory

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

Article information

Article type
Paper
Submitted
15 Jan 2016
Accepted
08 Feb 2016
First published
15 Feb 2016
This article is Open Access
Creative Commons BY license

Phys. Chem. Chem. Phys., 2016,18, 21001-21009

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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