<i>Ab initio</i> path integral Monte Carlo simulations of warm dense two-component systems without fixed nodes: Structural properties

Dornheim, Tobias; Schwalbe, Sebastian; Böhme, Maximilian P.; Moldabekov, Zhandos A.; Vorberger, Jan; Tolias, Panagiotis

doi:10.1063/5.0206787

The Journal of Chemical Physics

2024

DOI: 10.1063/5.0206787

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Ab initio path integral Monte Carlo simulations of warm dense two-component systems without fixed nodes: Structural properties

Tobias Dornheim,

Sebastian Schwalbe,

Maximilian P. Böhme

et al.

Abstract: We present extensive new ab initio path integral Monte Carlo (PIMC) results for a variety of structural properties of warm dense hydrogen and beryllium. To deal with the fermion sign problem—an exponential computational bottleneck due to the antisymmetry of the electronic thermal density matrix—we employ the recently proposed [Y. Xiong and H. Xiong, J. Chem. Phys. 157, 094112 (2022); T. Dornheim et al., J. Chem. Phys. 159, 164113 (2023)] ξ-extrapolation method and find excellent agreement with the exact direct… Show more

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2024

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Cited by 3 publications

References 157 publications

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Ensemble Generalization of the Perdew–Zunger Self-Interaction Correction: A Way Out of Multiple Minima and Symmetry Breaking

Schwalbe,

Schulze,

Trepte

et al. 2024

J. Chem. Theory Comput.

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The Perdew–Zunger (PZ) self-interaction correction (SIC) is an established tool to correct unphysical behavior in density functional approximations. Yet, the PZ-SIC is well-known to sometimes break molecular symmetries. An example of this is the benzene molecule, for which the PZ-SIC predicts a symmetry-broken electron density and molecular geometry, since the method does not describe the two possible Kekulé structures on an even footing, leading to local minima [J. Chem. Theory Comput.2016123195]. The PZ-SIC is often implemented with Fermi–Löwdin orbitals (FLOs), yielding the FLO-SIC method, which likewise has issues with symmetry breaking and local minima [J. Chem. Phys.2021155224109]. In this work, we propose a generalization of the PZ-SICthe ensemble PZ-SIC (E-PZ-SIC) methodwhich shares the asymptotic computational scaling of the PZ-SIC (albeit with an additional prefactor). The E-PZ-SIC is straightforwardly applicable to various molecules, merely requiring one to average the self-interaction correction over all possible Kekulé structures, in line with chemical intuition. We showcase the implementation of the E-PZ-SIC with FLOs, as the resulting E-FLO-SIC method is easy to realize on top of an existing implementation of the FLO-SIC. We show that the E-FLO-SIC indeed eliminates symmetry breaking, reproducing a symmetric electron density and molecular geometry for benzene. The ensemble approach suggested herein could also be employed within approximate or locally scaled variants of the PZ-SIC and its FLO-SIC versions.

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Ensemble Generalization of the Perdew–Zunger Self-Interaction Correction: A Way Out of Multiple Minima and Symmetry Breaking

Schwalbe,

Schulze,

Trepte

et al. 2024

J. Chem. Theory Comput.

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Ab initio density response and local field factor of warm dense hydrogen

Dornheim,

Schwalbe,

Tolias

et al. 2024

Matter and Radiation at Extremes

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We present quasi-exact ab initio path integral Monte Carlo (PIMC) results for the partial static density responses and local field factors of hydrogen in the warm dense matter regime, from solid density conditions to the strongly compressed case. The full dynamic treatment of electrons and protons on the same footing allows us to rigorously quantify both electronic and ionic exchange–correlation effects in the system, and to compare the results with those of earlier incomplete models such as the archetypal uniform electron gas or electrons in a fixed ion snapshot potential that do not take into account the interplay between the two constituents. The full electronic density response is highly sensitive to electronic localization around the ions, and our results constitute unambiguous predictions for upcoming X-ray Thomson scattering experiments with hydrogen jets and fusion plasmas. All PIMC results are made freely available and can be used directly for a gamut of applications, including inertial confinement fusion calculations and the modeling of dense astrophysical objects. Moreover, they constitute invaluable benchmark data for approximate but computationally less demanding approaches such as density functional theory or PIMC within the fixed-node approximation.

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Dynamic exchange correlation effects in the strongly coupled electron liquid

Dornheim,

Tolias,

Kalkavouras

et al. 2024

Phys. Rev. B

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The first quasiexact path integral Monte Carlo (PIMC) investigation of the dynamic local field correction G̃(q,zl;rs,Θ) in the imaginary Matsubara frequency domain is reported, focusing on the unpolarized uniform electron gas in the warm dense matter and strongly coupled regimes. The impact of dynamic exchange–correlation effects on the static structure factor is investigated. A straightforward explanation is provided for previously reported spurious effects in the so-called [Dornheim , ], where the frequency dependence of the local field correction is neglected. The comprehensive analysis of the asymptotic Matsubara order behavior, the density dependence, and the temperature dependence hints at the intriguing possibility of constructing an analytical four-parameter representation of G̃(q,zl;rs,Θ) valid for a substantial part of the uniform electron gas phase diagram, which would constitute key input for thermal density functional theory simulations. Published by the American Physical Society 2024

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Ab initio path integral Monte Carlo simulations of warm dense two-component systems without fixed nodes: Structural properties

Cited by 3 publications

References 157 publications

Ensemble Generalization of the Perdew–Zunger Self-Interaction Correction: A Way Out of Multiple Minima and Symmetry Breaking

Ensemble Generalization of the Perdew–Zunger Self-Interaction Correction: A Way Out of Multiple Minima and Symmetry Breaking

Ab initio density response and local field factor of warm dense hydrogen

Dynamic exchange correlation effects in the strongly coupled electron liquid

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