Tight constraints on the exchange-correlation potentials of degenerate states

Paul W Ayers; Mel Levy

doi:10.1063/1.4871732

Tight constraints on the exchange-correlation potentials of degenerate states

J Chem Phys. 2014 May 14;140(18):18A537. doi: 10.1063/1.4871732.

Authors

Paul W Ayers¹, Mel Levy²

Affiliations

¹ Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario L8S4M1, Canada.
² Department of Chemistry, Duke University, Durham, North Carlina 27708, USA.

PMID: 24832345
DOI: 10.1063/1.4871732

Abstract

Identities for the difference of exchange-correlation potentials and energies in degenerate and nondegenerate ground states are derived. The constraints are strong for degenerate ground states, and suggest that local and semilocal approximations to the exchange-correlation energy functional are incapable of correctly treating degenerate ground states. For degenerate states, it is possible to provide both local (pointwise) equality and global inequality constraints for the exchange-correlation potential in terms of the Coulomb potential.