Condensed Matter Seminar Series
The Discontinuous Nature of the Exchange- Correlation Functional: Critical for Strongly Correlated Systems
Duke University (Chemistry)
Thursday February 5, 11:00 am, Room 298, Physics Building
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 to understand the physics of strongly correlated systems within
DFT, for example the band-gap of Mott insulators.
Host: Harold Baranger