1210.8300 (Fabio Caruso et al.)

Bond breaking and bond formation: how electron correlation is captured
in many-body perturbation theory and density-functional theory    [PDF]

Fabio Caruso, Daniel Rohr, Maria Hellgren, Xinguo Ren, Patrick Rinke, Angel Rubio, Matthias Scheffler

For the paradigmatic case of H2-dissociation we compare state-of-the-art many-body perturbation theory (MBPT) in the GW approximation and density-functional theory (DFT) in the exact-exchange plus random-phase approximation for the correlation energy (EX+cRPA). For an unbiased comparison and to prevent spurious starting point effects both approaches are iterated to full self-consistency (i.e. sc-RPA and sc-GW). The exchange-correlation diagrams in both approaches are topologically identical, but in sc-RPA they are evaluated with non-interacting and in sc-GW with interacting Green functions. This has a profound consequence for the dissociation region, where sc-RPA is superior to sc-GW. We argue that for a given diagrammatic expansion, the DFT framework outperforms the many-body framework when it comes to bond-breaking. We attribute this to the difference in the correlation energy rather than the treatment of the kinetic energy.

View original: http://arxiv.org/abs/1210.8300