Does an exact local exchange potential exist

Abstract

In Kohn–Sham density functional theory, equations for occupied orbital functions of a model state are derived from the exact ground‐state energy functional of Hohenberg and Kohn. The exchange‐correlation potential in these exact Kohn–Sham equations is commonly assumed to be a local potential function rather than a more general linear operator. This assumption is tested and shown to fail for the exchange potential in a Hartree–Fock model for atoms, for which accurate solutions are known.