Double excitations within time-dependent density functional theory linear response.
Within the adiabatic approximation, time-dependent density functional theory yields only single excitations. Near states of double excitation character, the exact exchange-correlation kernel has a strong dependence on frequency. We derive the exact frequency-dependent kernel when a double excitation mixes with a single excitation, well separated from the other excitations, in the limit that the electron--electron interaction is weak. Building on this, we construct a nonempirical approximation for the general case, and illustrate our results on a simple model.
Maitra
Neepa T
NT
Department of Physics and Astronomy, City University of New York and Hunter College, New York, New York 10021, USA. nmaitra@hunter.cuny.edu
Zhang
Fan
F
Cave
Robert J
RJ
Burke
Kieron
K