Broadening of the derivative discontinuity in density functional theory

Phys Chem Chem Phys. 2011 Aug 28;13(32):14417-20. doi: 10.1039/c1cp21247h. Epub 2011 Jul 27.

Abstract

We clarify an important aspect of density functional theories, the broadening of the derivative discontinuity (DD) in a quantum system, with fluctuating particle number. Our focus is on a correlated model system, the single level quantum dot in the regime of the Coulomb blockade. We find that the DD-broadening is controlled by the small parameter Γ/U, where Γ is the level broadening due to contacting and U is a measure of the charging energy. Our analysis suggests that Kondoesque fluctuations have a tendency to increase the DD-broadening in our model by a factor of two.