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Article Dans Une Revue Frontiers in Chemistry Année : 2021

Scrutinizing GW-Based Methods Using the Hubbard Dimer

Stefano Di Sabatino
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Pierre-Francois Loos

Résumé

Using the simple (symmetric) Hubbard dimer, we analyze some important features of the $GW$ approximation. We show that the problem of the existence of multiple quasiparticle solutions in the (perturbative) one-shot $GW$ method and its partially self-consistent version is solved by full self-consistency. We also analyze the neutral excitation spectrum using the Bethe-Salpeter equation (BSE) formalism within the standard $GW$ approximation and find, in particular, that i) some neutral excitation energies become complex when the electron-electron interaction $U$ increases, which can be traced back to the approximate nature of the $GW$ quasiparticle energies; ii) the BSE formalism yields accurate correlation energies over a wide range of $U$ when the trace (or plasmon) formula is employed; iii) the trace formula is sensitive to the occurrence of complex excitation energies (especially singlet), while the expression obtained from the adiabatic-connection fluctuation-dissipation theorem (ACFDT) is more stable (yet less accurate); iv) the trace formula has the correct behavior for weak (\ie, small $U$) interaction, unlike the ACFDT expression.
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Dates et versions

hal-03315304 , version 1 (09-09-2021)

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Stefano Di Sabatino, Pierre-Francois Loos, Pina Romaniello. Scrutinizing GW-Based Methods Using the Hubbard Dimer. Frontiers in Chemistry, 2021, 9, pp.751054. ⟨10.3389/fchem.2021.751054⟩. ⟨hal-03315304⟩
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