Static correlation and electron localization in molecular dimers from the self-consistent RPA and GW approximation
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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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Physical Review B, Volume 91, issue 16, pp. 1-12
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
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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