TY - JOUR
T1 - Fractional occupation in Kohn-Sham density-functional theory and the treatment of non-pure-state v -representable densities
AU - Kraisler, Eli
AU - Makov, Guy
AU - Argaman, Nathan
AU - Kelson, Itzhak
PY - 2009/9/24
Y1 - 2009/9/24
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=70349494211&partnerID=8YFLogxK
U2 - 10.1103/PhysRevA.80.032115
DO - 10.1103/PhysRevA.80.032115
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AN - SCOPUS:70349494211
SN - 1050-2947
VL - 80
JO - Physical Review A - Atomic, Molecular, and Optical Physics
JF - Physical Review A - Atomic, Molecular, and Optical Physics
IS - 3
M1 - 032115
ER -