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arXiv · 1011.4564

Fractional occupation in Kohn-Sham density-functional theory and the treatment of non-pure-state v-representable densities

Eli Kraisler·Guy Makov·Nathan Argaman·Itzhak Kelson
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Abstract

In the framework of Kohn-Sham density-functional theory, systems with ground-state densities that are not pure-state v-representable in the non-interacting reference system (PSVR) occur frequently. In the present contribution, a new algorithm, which allows the solution of such systems, is proposed. It is shown that the use of densities which do not correspond to a ground state of their non-interacting reference system is forbidden. As a consequence, the proposed algorithm considers only non-interacting ensemble v-representable densities. The Fe atom, a well-known non-PSVR system, is used as an illustration. Finally, the problem is analyzed within finite temperature density-functional theory, where the physical significance of fractional occupations is exposed and the question of why degenerate states can be unequally occupied is resolved.

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Eli Kraisler, Guy Makov, Nathan Argaman, Itzhak Kelson. 2010-11-20. Fractional occupation in Kohn-Sham density-functional theory and the treatment of non-pure-state v-representable densities. https://doi.org/10.1103/physreva.80.032115

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