Unphysical Discontinuities in <i>GW</i> Methods

Véril, Mickaël; Romaniello, Pina; Berger, J. A.; Loos, Pierre‐François

doi:10.1021/acs.jctc.8b00745

Cited by 47 publications

(56 citation statements)

References 106 publications

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“…In these cases, the quasiparticle equation can have multiple solutions, making both the GW calculation and interpretation of the result more difficult. The problem also appears for more conventional valence states of small molecules, and recent work has shown that these multiple solutions lead to unphysical discontinuities in quasiparticle energies and that ev GW can exacerbate the problem (Loos et al, 2018; Véril et al, 2018). Just as for experimental spectroscopy, the sensitivity of core states to the local environment makes the GW calculation more challenging than for conventional valence states.…”

Section: Current Challenges and Beyond Gwmentioning

confidence: 99%

The GW Compendium: A Practical Guide to Theoretical Photoemission Spectroscopy

2019

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The GW approximation in electronic structure theory has become a widespread tool for predicting electronic excitations in chemical compounds and materials. In the realm of theoretical spectroscopy, the GW method provides access to charged excitations as measured in direct or inverse photoemission spectroscopy. The number of GW calculations in the past two decades has exploded with increased computing power and modern codes. The success of GW can be attributed to many factors: favorable scaling with respect to system size, a formal interpretation for charged excitation energies, the importance of dynamical screening in real systems, and its practical combination with other theories. In this review, we provide an overview of these formal and practical considerations. We expand, in detail, on the choices presented to the scientist performing GW calculations for the first time. We also give an introduction to the many-body theory behind GW , a review of modern applications like molecules and surfaces, and a perspective on methods which go beyond conventional GW calculations. This review addresses chemists, physicists and material scientists with an interest in theoretical spectroscopy. It is intended for newcomers to GW calculations but can also serve as an alternative perspective for experts and an up-to-date source of computational techniques.

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Section: Current Challenges and Beyond Gwmentioning

confidence: 99%

The GW Compendium: A Practical Guide to Theoretical Photoemission Spectroscopy

2019

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“… 42 Multiple solutions have been reported for a couple of systems. 42 , 47 − 49 However, typically not more than two possible solutions were found, whereas a multitude of peaks are observed in the spectral function of molecular 1s states at the G 0 W 0 @ PBE level without exception.…”

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confidence: 99%

Accurate Absolute and Relative Core-Level Binding Energies from GW

Golze

Keller

Rinke

2020

J. Phys. Chem. Lett.

108

258

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We present an accurate approach to compute X-ray photoelectron spectra based on the GW Green's function method, that overcomes shortcomings of common density functional theory approaches. GW has become a popular tool to compute valence excitations for a wide range of materials. However, core-level spectroscopy is thus far almost uncharted in GW. We show that single-shot perturbation calculations in the G 0 W 0 approximation, which are routinely used for valence states, cannot be applied for core levels and suffer from an extreme, erroneous transfer of spectral weight to the satellite spectrum. The correct behavior can be restored by partial self-consistent GW schemes or by using hybrid functionals with almost 50% of exact exchange as starting point for G 0 W 0 . We include also relativistic corrections and present a benchmark study for 65 molecular 1s excitations. Our absolute and relative GW core-level binding energies agree within 0.3 and 0.2 eV with experiment, respectively.

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“…However, we also observe that, in some cases, unphysical irregularities on the ground-state PES, which are due to the appearance of a satellite resonance with a weight similar to that of the GW quasiparticle peak. [78][79][80][81][82] In order to compute the neutral (optical) excitations of the system and their associated oscillator strengths, the BSE expresses the two-body propagator 4,83 L(1, 2, 1 , 2 ) = L 0 (1, 2, 1 , 2 )…”

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confidence: 99%

“…This shortcoming has been thoroughly described in several previous studies. [78][79][80][81][82] We believe that this central issue must be resolved if one wants to expand the applicability of the present method.…”

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confidence: 99%

Pros and Cons of the Bethe–Salpeter Formalism for Ground-State Energies

Loos

Scemama

Duchemin

et al. 2020

J. Phys. Chem. Lett.

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The combination of the many-body Green's function GW approximation and the Bethe-Salpeter equation (BSE) formalism has shown to be a promising alternative to time-dependent density-functional theory (TD-DFT) for computing vertical transition energies and oscillator strengths in molecular systems. The BSE formalism can also be employed to compute ground-state correlation energies thanks to the adiabatic-connection fluctuationdissipation theorem (ACFDT). Here, we study the topology of the ground-state potential energy surfaces (PES) of several diatomic molecules near their equilibrium bond length. Thanks to comparisons with state-of-art computational approaches (CC3), we show that ACFDT@BSE is surprisingly accurate, and can even compete with lower-order coupled cluster methods (CC2 and CCSD) in terms of total energies and equilibrium bond distances for the considered systems. However, we sometimes observe unphysical irregularities on the groundstate PES in relation with difficulties in the identification of a few GW quasiparticle energies.

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Unphysical Discontinuities in GW Methods

Cited by 47 publications

References 106 publications

The GW Compendium: A Practical Guide to Theoretical Photoemission Spectroscopy

The GW Compendium: A Practical Guide to Theoretical Photoemission Spectroscopy

Accurate Absolute and Relative Core-Level Binding Energies from GW

Pros and Cons of the Bethe–Salpeter Formalism for Ground-State Energies

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