Beyond time-dependent exact exchange: The need for long-range correlation
|Title||Beyond time-dependent exact exchange: The need for long-range correlation|
|Publication Type||Palaiseau Article|
|Author Address|| |
Bruneval, F (Reprint Author), Ecole Polytech, European Theoret Spect Facil, Solides Irradies Lab, CNRS,UMR 7642,CEA,DSM, F-91128 Palaiseau, France. Ecole Polytech, European Theoret Spect Facil, Solides Irradies Lab, CNRS,UMR 7642,CEA,DSM, F-91128 Palaiseau, France. DIPC, Donostia An Sebastian 20018, Spain. CNRS, UPR 11, Etud Proprietes Elect Solides Lab, F-38042 Grenoble, France.
|Bruneval, F, Sottile, F, Olevano, V, Reining, L|
|Year of Publication||2006|
|Journal||J. Chem. Phys.|
In the description of the interaction between electrons beyond the classical Hartree picture, bare exchange often yields a leading contribution. Here we discuss its effect on optical spectra of solids, comparing three different frameworks: time-dependent Hartree-Fock, a recently introduced combined density-functional and Green's function approaches applied to the bare exchange self-energy, and time-dependent exact exchange within time-dependent density-functional theory (TD-EXX). We show that these three approximations give rise to identical excitonic effects in solids; these effects are drastically overestimated for semiconductors. They are partially compensated by the usual overestimation of the quasiparticle band gap within Hartree-Fock. The physics that lacks in these approaches can be formulated as screening. We show that the introduction of screening in TD-EXX indeed leads to a formulation that is equivalent to previously proposed functionals derived from many-body perturbation theory. It can be simulated by reducing the long-range part of the Coulomb interaction: this produces absorption spectra of semiconductors in good agreement with experiment. (c) 2006 American Institute of Physics.