Degenerate ground states and a fractional number of electrons in density and reduced density matrix functional theory

Weitao Yang, Yingkai Zhang, Paul W. Ayers

Research output: Contribution to journalArticle

Abstract

For a linear combination of electron densities of degenerate ground states, it is shown that the value of any energy functional is the ground state energy, if the energy functional is exact for ground state densities, size consistent, and translational invariant. The corresponding functional of kinetic and interaction energy is the linear combination of the functionals of the degenerate densities. Without invoking ensembles, it is shown that the energy functional of fractional number electrons is a series of straight lines interpolating its values at integers. These results underscore the importance of grand canonical ensemble formulation in density functional theory.

Original languageEnglish (US)
Pages (from-to)5172-5175
Number of pages4
JournalPhysical Review Letters
Volume84
Issue number22
DOIs
StatePublished - 2000

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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