Article

# Adiabatic connection for strictly correlated electrons.

Department of Chemistry, University of California, Irvine, California 92697-2025, USA.

The Journal of Chemical Physics (Impact Factor: 3.12). 09/2009; 131(12):124124. DOI: 10.1063/1.3239472 Source: arXiv

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**ABSTRACT:**Anions and radicals are important for many applications including environmental chemistry, semiconductors, and charge transfer, but are poorly described by the available approximate energy density functionals. Here we test an approximate exchange-correlation functional based on the exact strong-coupling limit of the Hohenberg-Kohn functional on the prototypical case of the He isoelectronic series with varying nuclear charge Z < 2, which includes weakly bound negative ions and a quantum phase transition at a critical value of Z, representing a big challenge for density functional theory. We use accurate wavefunction calculations to validate our results, comparing energies and Kohn-Sham potentials, thus also providing useful reference data close to and at the quantum phase transition. We show that our functional is able to bind H(-) and to capture in general the physics of loosely bound anions, with a tendency to strongly overbind that can be proven mathematically. We also include corrections based on the uniform electron gas which improve the results.The Journal of Chemical Physics 05/2014; 140(18):18A532. · 3.12 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**We use the exact strong-interaction limit of the Hohenberg-Kohn energy density functional to approximate the exchange-correlation energy of the restricted Kohn-Sham scheme. Our approximation corresponds to a highly nonlocal density functional whose functional derivative can be easily constructed, thus transforming exactly, in a physically transparent way, an important part of the electron-electron interaction into an effective local one-body potential. We test our approach on quasi-one-dimensional systems, showing that it captures essential features of strong correlation that restricted Kohn-Sham calculations using the currently available approximations cannot describe.Physical Review Letters 12/2012; 109(24):246402. · 7.73 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**We study one-dimensional model chemical systems (representative of their three-dimensional counterparts) using the strictly-correlated electron (SCE) functional, which, by construction, becomes asymptotically exact in the limit of infinite coupling strength. The SCE functional has a highly non-local dependence on the density and is able to capture strong correlation within the Kohn-Sham theory without introducing any symmetry breaking. Chemical systems, however, are not close enough to the strong-interaction limit so that, while ionization energies and the stretched H2 molecule are accurately described, total energies are in general too low. A correction based on the exact next leading order in the expansion at infinite coupling strength of the Hohenberg-Kohn functional largely improves the results.Physical Chemistry Chemical Physics 04/2014; · 4.20 Impact Factor

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