
Physics 2011
Koopmans' theorem in statistical HartreeFock theoryDOI: 10.1088/09534075/44/14/145001 Abstract: In this short paper, the validity of Koopmans' theorem in the HartreeFock theory at nonzero temperature (HartreeFock statistical theory) is investigated. It is shown that Koopmans' theorem does not apply in the grandcanonical ensemble, due to a missing contribution to the energy proportional to the interaction between two electrons belonging to the same orbital. HartreeFock statistical theory has also been applied in the canonical ensemble [Blenski et al., Phys. Rev. E 55, R4889 (1997)] for the purpose of photoabsorption calculations. In that case, the HartreeFock selfconsistentfield equations are derived in the superconfiguration approximation. It is shown that Koopmans' theorem does not hold in the canonical ensemble, but that a restricted version of the theorem can be obtained, by assuming that a particular quantity multiplying the interaction matrix element in the expression of the energy does not change during the removal of an electron.
