The discontinuous nature of the exchange-correlation functional -- critical for strongly correlated systems

Abstract

Standard approximations for the exchange-correlation functional have been found to give big errors for the linearity condition of fractional charges, leading to delocalization error, and the constancy condition of fractional spins, leading to static correlation error. These two conditions are now unified for states with both fractional charge and fractional spin: the exact energy functional is a plane, linear along the fractional charge coordinate and constant along the fractional spin coordinate with a line of discontinuity at the integer. This sheds light on the nature of the derivative discontinuity and calls for explicitly discontinuous functionals of the density or orbitals that go beyond currently used smooth approximations. This is key for the application of DFT to strongly correlated systems.

5 pages 2 figures

References in corpus (5)

• Localization and delocalization errors in density functional theory and implications for band-gap prediction
• Fractional charge perspective on the band-gap in density-functional theory
• Fractional spins and static correlation error in density functional theory
• Reduced Density Matrix Functional for Many-Electron Systems
• Exchange and Correlation in Open Systems of Fluctuating Electron Number

Cited by in corpus (1)

• Towards the parameterisation of the Hubbard model for salts of BEDT-TTF: A density functional study of isolated molecules