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Issue 6, 2017
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Electron correlation effects in third-order densities

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The electronic energy of a system of fermions can be obtained from the second-order reduced density matrix through the contracted Schrödinger equation or its anti-Hermitian counterpart. Both energy expressions depend on the third-order reduced density matrix (3-RDM) which is usually approximated from lower-order densities. The accuracy of these methods depends critically on the set of N-representability conditions enforced in the calculation and the quality of the approximate 3-RDM. There are no benchmark studies including most 3-RDM approximations and, thus far, no assessment of the deterioration of the approximations with correlation effects has been performed. In this paper we introduce a series of tests to assess the performance of 3-RDM approximations in a model system with varying electron correlation effects, the three-electron harmonium atom. The results of this work put forward several limitations of the currently most used 3-RDM approximations for systems with important electron correlation effects.

Graphical abstract: Electron correlation effects in third-order densities

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The article was received on 07 Nov 2016, accepted on 04 Jan 2017 and first published on 09 Jan 2017

Article type: Paper
DOI: 10.1039/C6CP07616E
Citation: Phys. Chem. Chem. Phys., 2017,19, 4522-4529
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    Electron correlation effects in third-order densities

    M. Rodriguez-Mayorga, E. Ramos-Cordoba, F. Feixas and E. Matito, Phys. Chem. Chem. Phys., 2017, 19, 4522
    DOI: 10.1039/C6CP07616E

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