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Vacondio S, Varsano D, Ruini A, Ferretti A. Going Beyond the GW Approximation Using the Time-Dependent Hartree-Fock Vertex. J Chem Theory Comput 2024; 20:4718-4737. [PMID: 38772396 DOI: 10.1021/acs.jctc.4c00100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/23/2024]
Abstract
The time-dependent Hartree-Fock (TDHF) vertex of many-body perturbation theory (MBPT) makes it possible to extend TDHF theory to charged excitations. Here we assess its performance by applying it to spherical atoms in their neutral electronic configuration. On a theoretical level, we recast the TDHF vertex as a reducible vertex, highlighting the emergence of a self-energy expansion purely in orders of the bare Coulomb interaction; then, on a numerical level, we present results for polarizabilities, ionization energies (IEs), and photoemission satellites. We confirm the superiority of THDF over simpler methods such as the random phase approximation for the prediction of atomic polarizabilities. We then find that the TDHF vertex reliably provides better IEs than GW and low-order self-energies do in the light-atom, few-electron regime; its performance degrades in heavier, many-electron atoms instead, where an expansion in orders of an unscreened Coulomb interaction becomes less justified. New relevant features are introduced in the satellite spectrum by the TDHF vertex, but the experimental spectra are not fully reproduced due to a missing account of nonlinear effects connected to hole relaxation. We also explore various truncations of the self-energy given by the TDHF vertex, but do not find them to be more convenient than low-order approximations such as GW and second Born (2B), suggesting that vertex corrections should be carried out consistently both in the self-energy and in the polarizability.
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Affiliation(s)
- Simone Vacondio
- Dipartimento di Scienze Fisiche, Informatiche e Matematiche, Università degli Studi di Modena e Reggio Emilia, Via G. Campi 213/a, 41125 Modena, Italy
- Centro S3, CNR-Istituto Nanoscienze, Via G. Campi 213/a, 41125 Modena, Italy
| | - Daniele Varsano
- Centro S3, CNR-Istituto Nanoscienze, Via G. Campi 213/a, 41125 Modena, Italy
| | - Alice Ruini
- Dipartimento di Scienze Fisiche, Informatiche e Matematiche, Università degli Studi di Modena e Reggio Emilia, Via G. Campi 213/a, 41125 Modena, Italy
- Centro S3, CNR-Istituto Nanoscienze, Via G. Campi 213/a, 41125 Modena, Italy
| | - Andrea Ferretti
- Centro S3, CNR-Istituto Nanoscienze, Via G. Campi 213/a, 41125 Modena, Italy
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2
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Bruneval F, Förster A. Fully Dynamic G3 W2 Self-Energy for Finite Systems: Formulas and Benchmark. J Chem Theory Comput 2024; 20:3218-3230. [PMID: 38603811 DOI: 10.1021/acs.jctc.4c00090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/13/2024]
Abstract
Over the years, Hedin's GW self-energy has been proven to be a rather accurate and simple approximation to evaluate electronic quasiparticle energies in solids and in molecules. Attempts to improve over the simple GW approximation, the so-called vertex corrections, have been constantly proposed in the literature. Here, we derive, analyze, and benchmark the complete second-order term in the screened Coulomb interaction W for finite systems. This self-energy named G3W2 contains all the possible time orderings that combine 3 Green's functions G and 2 dynamic W. We present the analytic formula and its imaginary frequency counterpart, with the latter allowing us to treat larger molecules. The accuracy of the G3W2 self-energy is evaluated on well-established benchmarks (GW100, Acceptor 24, and Core 65) for valence and core quasiparticle energies. Its link with the simpler static approximation, named SOSEX for static screened second-order exchange, is analyzed, which leads us to propose a more consistent approximation named 2SOSEX. In the end, we find that neither the G3W2 self-energy nor any of the investigated approximations to it improve over one-shot G0W0 with a good starting point. Only quasi-particle self-consistent GW HOMO energies are slightly improved by addition of the G3W2 self-energy correction. We show that this is due to the self-consistent update of the screened Coulomb interaction, leading to an overall sign change of the vertex correction to the frontier quasiparticle energies.
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Affiliation(s)
- Fabien Bruneval
- Université Paris-Saclay, CEA, Service de recherche en Corrosion et Comportement des Matériaux, SRMP, 91191 Gif-sur-Yvette, France
| | - Arno Förster
- Theoretical Chemistry, Vrije Universiteit, De Boelelaan 1108, 1081 HZ Amsterdam, The Netherlands
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3
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El-Sahili A, Sottile F, Reining L. Total Energy beyond GW: Exact Results and Guidelines for Approximations. J Chem Theory Comput 2024; 20:1972-1987. [PMID: 38324673 DOI: 10.1021/acs.jctc.3c01200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2024]
Abstract
The total energy and electron addition and removal spectra can, in principle, be obtained exactly from the one-body Green's function (GF). In practice, the GF is obtained from an approximate self-energy. In the framework of many-body perturbation theory, we derive different expressions that are based on an approximate self-energy, but that yield nevertheless, in principle, the exact exchange-correlation contribution to the total energy for any interaction strength. Response functions play a crucial role, which explains why, for example, ingredients from time-dependent density functional theory can be used to build these approximate self-energies. We show that the key requirement for obtaining exact results is the consistent combination of ingredients. Also when further approximations are made, as it is necessary in practice, this consistency remains the key to obtain good results. All findings are illustrated using the exactly solvable symmetric Hubbard dimer.
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Affiliation(s)
- Abdallah El-Sahili
- LSI, CNRS, CEA/DRF/IRAMIS, École Polytechnique, Institut Polytechnique de Paris, Palaiseau F-91120, France
- European Theoretical Spectroscopy Facility (ETSF), https://www.etsf.eu/
| | - Francesco Sottile
- LSI, CNRS, CEA/DRF/IRAMIS, École Polytechnique, Institut Polytechnique de Paris, Palaiseau F-91120, France
- European Theoretical Spectroscopy Facility (ETSF), https://www.etsf.eu/
| | - Lucia Reining
- LSI, CNRS, CEA/DRF/IRAMIS, École Polytechnique, Institut Polytechnique de Paris, Palaiseau F-91120, France
- European Theoretical Spectroscopy Facility (ETSF), https://www.etsf.eu/
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Vacondio S, Varsano D, Ruini A, Ferretti A. Numerically Precise Benchmark of Many-Body Self-Energies on Spherical Atoms. J Chem Theory Comput 2022; 18:3703-3717. [PMID: 35561415 PMCID: PMC9202310 DOI: 10.1021/acs.jctc.2c00048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
We investigate the
performance of beyond-GW approaches in many-body
perturbation theory by addressing atoms described within the spherical
approximation via a dedicated numerical treatment based on B-splines
and spherical harmonics. We consider the GW, second Born (2B), and
GW + second order screened exchange (GW+SOSEX) self-energies and use
them to obtain ionization potentials from the quasi-particle equation
(QPE) solved perturbatively on top of independent-particle calculations.
We also solve the linearized Sham–Schlüter equation
(LSSE) and compare the resulting xc potentials against exact data.
We find that the LSSE provides consistent starting points for the
QPE but does not present any practical advantage in the present context.
Still, the features of the xc potentials obtained with it shed light
on possible strategies for the inclusion of beyond-GW diagrams in
the many-body self-energy. Our findings show that solving the QPE
with the GW+SOSEX self-energy on top of a PBE or PBE0 solution is
a viable scheme to go beyond GW in finite systems, even in the atomic
limit. However, GW shows a comparable performance if one agrees to
use a hybrid starting point. We also obtain promising results with
the 2B self-energy on top of Hartree–Fock, suggesting that
the full time-dependent Hartree–Fock vertex may be another
viable beyond-GW scheme for finite systems.
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Affiliation(s)
- S Vacondio
- Dipartimento di Scienze Fisiche, Informatiche e Matematiche, Università di Modena e Reggio Emilia, Via G. Campi 213/a, Modena 41121, Italy.,Centro S3, CNR-Istituto Nanoscienze, 41125 Modena, Italy
| | - D Varsano
- Centro S3, CNR-Istituto Nanoscienze, 41125 Modena, Italy
| | - A Ruini
- Dipartimento di Scienze Fisiche, Informatiche e Matematiche, Università di Modena e Reggio Emilia, Via G. Campi 213/a, Modena 41121, Italy.,Centro S3, CNR-Istituto Nanoscienze, 41125 Modena, Italy
| | - A Ferretti
- Centro S3, CNR-Istituto Nanoscienze, 41125 Modena, Italy
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Krien F, Kauch A. The plain and simple parquet approximation: single-and multi-boson exchange in the two-dimensional Hubbard model. THE EUROPEAN PHYSICAL JOURNAL. B 2022; 95:69. [PMID: 35531566 PMCID: PMC9023420 DOI: 10.1140/epjb/s10051-022-00329-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 04/01/2022] [Indexed: 06/14/2023]
Abstract
Abstract The parquet approach to vertex corrections is unbiased but computationally demanding. Most applications are therefore restricted to small cluster sizes or rely on various simplifying approximations. We have recently shown that the bosonization of the parquet diagrams provides interpretative and algorithmic advantages over the original purely fermionic formulation. Here, we present first results of the numerical implementation of this method by applying it to the half-filled Hubbard model on the square lattice at weak coupling. The improved algorithmic performance allows us to evaluate the parquet approximation for a 16 × 16 lattice, retaining the full momentum and frequency structure of the various vertex functions. We discuss their symmetries and consider parametrizations of their momentum dependence using the truncated-unity approximation. Graphical abstract
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Affiliation(s)
- Friedrich Krien
- Institute of Solid State Physics, TU Wien, 1040 Vienna, Austria
| | - Anna Kauch
- Institute of Solid State Physics, TU Wien, 1040 Vienna, Austria
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Ismail-Beigi S. Justifying quasiparticle self-consistent schemes via gradient optimization in Baym-Kadanoff theory. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:385501. [PMID: 28593935 DOI: 10.1088/1361-648x/aa7803] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The question of which non-interacting Green's function 'best' describes an interacting many-body electronic system is both of fundamental interest as well as of practical importance in describing electronic properties of materials in a realistic manner. Here, we study this question within the framework of Baym-Kadanoff theory, an approach where one locates the stationary point of a total energy functional of the one-particle Green's function in order to find the total ground-state energy as well as all one-particle properties such as the density matrix, chemical potential, or the quasiparticle energy spectrum and quasiparticle wave functions. For the case of the Klein functional, our basic finding is that minimizing the length of the gradient of the total energy functional over non-interacting Green's functions yields a set of self-consistent equations for quasiparticles that is identical to those of the quasiparticle self-consistent GW (QSGW) (van Schilfgaarde et al 2006 Phys. Rev. Lett. 96 226402-4) approach, thereby providing an a priori justification for such an approach to electronic structure calculations. In fact, this result is general, applies to any self-energy operator, and is not restricted to any particular approximation, e.g., the GW approximation for the self-energy. The approach also shows that, when working in the basis of quasiparticle states, solving the diagonal part of the self-consistent Dyson equation is of primary importance while the off-diagonals are of secondary importance, a common observation in the electronic structure literature of self-energy calculations. Finally, numerical tests and analytical arguments show that when the Dyson equation produces multiple quasiparticle solutions corresponding to a single non-interacting state, minimizing the length of the gradient translates into choosing the solution with largest quasiparticle weight.
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Affiliation(s)
- Sohrab Ismail-Beigi
- Department of Applied Physics, Department of Physics, Department of Mechanical Engineering and Materials Science, and Center for Research on Interface Structures and Phenomena, Yale University, New Haven, CT 06520, United States of America
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7
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Pavlyukh Y. Padé resummation of many-body perturbation theories. Sci Rep 2017; 7:504. [PMID: 28356576 PMCID: PMC5428253 DOI: 10.1038/s41598-017-00355-w] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Accepted: 02/21/2017] [Indexed: 11/17/2022] Open
Abstract
In a typical scenario the diagrammatic many-body perturbation theory generates asymptotic series. Despite non-convergence, the asymptotic expansions are useful when truncated to a finite number of terms. This is the reason for the popularity of leading-order methods such as the GW approximation in condensed matter, molecular and atomic physics. Appropriate truncation order required for the accurate description of strongly correlated materials is, however, not known a priori. Here an efficient method based on the Padé approximation is introduced for the regularization of perturbative series allowing to perform higher-order self-consistent calculations and to make quantitative predictions on the convergence of many-body perturbation theories. The theory is extended towards excited states where the Wick theorem is not directly applicable. Focusing on the plasmon-assisted photoemission from graphene, we treat diagrammatically electrons coupled to the excited state plasmons and predict new spectral features that can be observed in the time-resolved measurements.
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Affiliation(s)
- Y Pavlyukh
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, P.O. Box 3049, 67653, Kaiserslautern, Germany. .,Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, 06120, Halle, Germany.
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McClain J, Sun Q, Chan GKL, Berkelbach TC. Gaussian-Based Coupled-Cluster Theory for the Ground-State and Band Structure of Solids. J Chem Theory Comput 2017; 13:1209-1218. [DOI: 10.1021/acs.jctc.7b00049] [Citation(s) in RCA: 130] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- James McClain
- Department
of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Qiming Sun
- Division
of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Garnet Kin-Lic Chan
- Division
of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Timothy C. Berkelbach
- Department
of Chemistry and James Franck Institute, University of Chicago, Chicago, Illinois 60637, United States
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