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

Loading...
Thumbnail Image
Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
This publication is imported from Aalto University research portal.
View publication in the Research portal
View/Open full text file from the Research portal
Date
2015
Major/Subject
Mcode
Degree programme
Language
en
Pages
1-12
Series
PHYSICAL REVIEW B, Volume 91, issue 16
Abstract
We investigate static correlation and delocalization errors in the self-consistent GW and random-phase approximation (RPA) by studying molecular dissociation of the H2 and LiH molecules. Although both approximations contain topologically identical diagrams, the nonlocality and frequency dependence of the GW self-energy crucially influence the different energy contributions to the total energy as compared to the use of a static local potential in the RPA. The latter leads to significantly 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 finite nuclear separation, their difference 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 formulas for the GW Green's function and total energy of a simplified two-level model providing additional insights into the dissociation limit.
Description
Keywords
GW, Hydrogen, RPA, static correlation
Other note
Citation
Hellgren, M, Caruso, F, Rohr, D R, Ren, X, Rubio, A, Scheffler, M & Rinke, P 2015, ' Static correlation and electron localization in molecular dimers from the self-consistent RPA and GW approximation ', Physical Review B, vol. 91, no. 16, 165110, pp. 1-12 . https://doi.org/10.1103/PhysRevB.91.165110