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Issue 21, 2012
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Fragment occupations in partition density functional theory

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The exact ground-state energy and density of a molecule can in principle be obtained via Partition Density Functional Theory (PDFT), a method for calculating molecular properties from Kohn–Sham calculations on isolated fragments. For a given choice of fragmentation, unique fragment densities are found by requiring that the sum of fragment energies be minimized subject to the constraint that the fragment densities sum to the correct molecular ground-state density. We investigate two interrelated aspects of PDFT: the connections between fragment densities obtained via different choices of fragmentation, for which we find “near-additivity”, and the nature of their corresponding fragment occupations. Whereas near-integer occupations arise for very large inter-fragment separations, strictly integer occupations appear for small inter-fragment separations. Cases where the fragment chemical potentials cannot be equalized lead to fragment occupations that lock into integers.

Graphical abstract: Fragment occupations in partition density functional theory

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Publication details

The article was received on 13 Dec 2011, accepted on 21 Mar 2012 and first published on 22 Mar 2012

Article type: Paper
DOI: 10.1039/C2CP23994A
Citation: Phys. Chem. Chem. Phys., 2012,14, 7780-7786

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    Fragment occupations in partition density functional theory

    R. Tang, J. Nafziger and A. Wasserman, Phys. Chem. Chem. Phys., 2012, 14, 7780
    DOI: 10.1039/C2CP23994A

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