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Issue 28, 2014
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Atomic electron affinities and the role of symmetry between electron addition and subtraction in a corrected Koopmans approach

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Abstract

The essential aspects of zero-temperature grand-canonical ensemble density-functional theory are reviewed in the context of spin-density-functional theory and are used to highlight the assumption of symmetry between electron addition and subtraction that underlies the corrected Koopmans approach of Tozer and De Proft (TDP) for computing electron affinities. The issue of symmetry is then investigated in a systematic study of atomic electron affinities, comparing TDP affinities with those from a conventional Koopmans evaluation and electronic energy differences. Although it cannot compete with affinities determined from energy differences, the TDP expression yields results that are a significant improvement over those from the conventional Koopmans expression. Key insight into the results from both expressions is provided by an analysis of plots of the electronic energy as a function of the number of electrons, which highlight the extent of symmetry between addition and subtraction. The accuracy of the TDP affinities is closely related to the nature of the orbitals involved in the electron addition and subtraction, being particularly poor in cases where there is a change in principal quantum number, but relatively accurate within a single manifold of orbitals. The analysis is then extended to a consideration of the ground state Mulliken electronegativity and chemical hardness. The findings further emphasize the key role of symmetry in determining the quality of the results.

Graphical abstract: Atomic electron affinities and the role of symmetry between electron addition and subtraction in a corrected Koopmans approach

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Publication details

The article was received on 26 Oct 2013, accepted on 23 Dec 2013 and first published on 02 Jan 2014


Article type: Paper
DOI: 10.1039/C3CP54528H
Citation: Phys. Chem. Chem. Phys., 2014,16, 14420-14434
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    Atomic electron affinities and the role of symmetry between electron addition and subtraction in a corrected Koopmans approach

    A. M. Teale, F. De Proft, P. Geerlings and D. J. Tozer, Phys. Chem. Chem. Phys., 2014, 16, 14420
    DOI: 10.1039/C3CP54528H

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