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

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

In the framework of Kohn-Sham density-functional theory, systems with ground-state densities that are not pure-state v -representable (PSVR) in the noninteracting reference system occur frequently. In the present contribution, an 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 noninteracting reference system is forbidden. As a consequence, the proposed algorithm considers only noninteracting 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.

Original languageEnglish
Article number032115
JournalPhysical Review A - Atomic, Molecular, and Optical Physics
Volume80
Issue number3
DOIs
StatePublished - 24 Sep 2009
Externally publishedYes

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