Abstract
This article is concerned with the mathematical analysis of the perturbation method for extended Kohn–Sham models, in which fractional occupation numbers are allowed. All our results are established in the framework of the reduced Hartree–Fock (rHF) model, but our approach can be used to study other kinds of Kohn–Sham models, under some assumptions on the mathematical structure of the exchange–correlation functional. The classical results of density functional perturbation theory in the non-degenerate case (that is when the Fermi level is not a degenerate eigenvalue of the mean-field Hamiltonian) are formalized, and a proof of Wigner's (2n + 1) rule is provided. We then focus on the situation when the Fermi level is a degenerate eigenvalue of the rHF Hamiltonian, which has not been considered so far.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
