Static correlation and electron localization in molecular dimers from the self-consistent RPA and GW approximation

Physical Review B 91, 165110 (2015)

Static correlation and electron localization in molecular dimers from the self-consistent RPA and GW approximation

M. Hellgren, F.Caruso, D.R. Rohr, X. Ren, A. Rubio, M. Scheffler, P. Rinke

We investigate static correlation and delocalization errors in the self-consistent GW and randomphase approximation (RPA) by studying molecular dissociation of the H2 and LiH molecules. Although both approximations contain topologically identical diagrams, the non-locality and frequency dependence of the GW self-energy crucially in uence the di erent energy contributions to the total energy as compared to the use of a static local potential in the RPA. The latter leads to signi cantly larger correlation energies which allow for a better description of static correlation at intermediate bond distances. The substantial error found in GW is further analyzed by comparing spin-restricted and spin-unrestricted calculations. At large but nite nuclear separation their di erence gives an estimate of the so-called fractional spin error normally determined only in the dissociation limit.Furthermore, a calculation of the dipole moment of the LiH molecule at dissociation reveals a large delocalization error in GW making the fractional charge error comparable to the RPA. The analyses are supplemented by explicit formulae for the GW Green's function and total energy of a simpli ed two-level model providing additional insights into the dissociation limit.

Additional Information

Download
Preprint - 801 KB
Doi
http://dx.doi.org/10.1103/PhysRevB.91.165110
Notes
AR acknowledges nancial support by the European Research Council Advanced Grant DYNamo (ERC-2010- AdG-267374), European Commission project CRONOS (Grant number 280879-2 CRONOS CP-FP7), Spanish Grant (FIS2013-46159-C3-1-P) and Grupos Consolidados UPV/EHU del Gobierno Vasco (IT578-13). PR acknowledges fi nancial support from the Academy of Finland through its Centres of Excellence Program (project no.251748).

Related Projects

Related Research Areas