Excited states from range-separated density-functional perturbation theory |
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Authors: | Elisa Rebolini Julien Toulouse Andrew M. Teale Trygve Helgaker Andreas Savin |
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Affiliation: | 1. Sorbonne Universités, UPMC Univ Paris 06, UMR 7616, Laboratoire de Chimie Théorique, Paris, France;2. CNRS, UMR 7616, Laboratoire de Chimie Théorique, Paris, France;3. Department of Chemistry, Centre for Theoretical and Computational Chemistry, University of Oslo, Oslo, Norwayerebolini@kjemi.uio.no;5. School of Chemistry, University of Nottingham, Nottingham, United Kingdomhttps://orcid.org/0000-0001-9617-1143;6. Department of Chemistry, Centre for Theoretical and Computational Chemistry, University of Oslo, Oslo, Norwayhttps://orcid.org/0000-0002-5032-8392 |
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Abstract: | We explore the possibility of calculating electronic excited states by using perturbation theory along a range-separated adiabatic connection. Starting from the energies of a partially interacting Hamiltonian, a first-order correction is defined with two variants of perturbation theory: a straightforward perturbation theory and an extension of the Görling–Levy one that has the advantage of keeping the ground-state density constant at each order in the perturbation. Only the first, simpler, variant is tested here on the helium and beryllium atoms and on the hydrogen molecule. The first-order correction within this perturbation theory improves significantly the total ground- and excited-state energies of the different systems. However, the excitation energies mostly deteriorate with respect to the zeroth-order ones, which may be explained by the fact that the ionisation energy is no longer correct for all interaction strengths. The second (Görling–Levy) variant of the perturbation theory should improve these results but has not been tested yet along the range-separated adiabatic connection. |
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Keywords: | excitation energies range separation perturbation theory adiabatic connection |
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