η-ensemble path integral Monte Carlo approach to the free energy of the warm dense electron gas and the uniform electron liquid

We explore the recently introduced η-ensemble approach to compute the free energy directly from ab initio path integral Monte Carlo (PIMC) simulations [T. Dornheim et al., Phys. Rev. B 111, L041114 (2025)2469-995010.1103/PhysRevB.111.L041114] and apply it to the archetypal uniform electron gas model...

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Main Authors: Tobias Dornheim, Panagiotis Tolias, Zhandos A. Moldabekov, Jan Vorberger
Format: Article
Language:English
Published: American Physical Society 2025-06-01
Series:Physical Review Research
Online Access:http://doi.org/10.1103/4n7x-78fs
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author Tobias Dornheim
Panagiotis Tolias
Zhandos A. Moldabekov
Jan Vorberger
author_facet Tobias Dornheim
Panagiotis Tolias
Zhandos A. Moldabekov
Jan Vorberger
author_sort Tobias Dornheim
collection DOAJ
description We explore the recently introduced η-ensemble approach to compute the free energy directly from ab initio path integral Monte Carlo (PIMC) simulations [T. Dornheim et al., Phys. Rev. B 111, L041114 (2025)2469-995010.1103/PhysRevB.111.L041114] and apply it to the archetypal uniform electron gas model both in the warm dense matter and strongly coupled regimes. Specifically, we present an in-depth study of the relevant algorithmic details such as the choice of the free weighting parameter and the choice of the optimum number of intermediate η-steps to connect the real, nonideal system (η=1) with the ideal limit (η=0). Moreover, we explore the inherent decomposition of the full free energy into its ideal bosonic, ideal-to-interacting, and bosonic-to-fermionic contributions for different parameter regimes. Finally, we compare our new free energy data with an existing free energy parametrization [Groth et al., Phys. Rev. Lett. 119, 135001 (2017)0031-900710.1103/PhysRevLett.119.135001] obtained via adiabatic connection formula evaluations, and we find very good agreement in its range of applicability, i.e., for density parameters r_{s}≤20; in addition, we present the first PIMC results for the free energy in the low density regime of 20<r_{s}≤100. We expect our results to be of interest both for the study of matter under extreme conditions, as well as to the more general field of PIMC simulations of interacting quantum many-body systems.
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spelling doaj-art-0990536ffcd04e5e9dbcefef375fe1602025-08-20T03:11:32ZengAmerican Physical SocietyPhysical Review Research2643-15642025-06-017202325010.1103/4n7x-78fsη-ensemble path integral Monte Carlo approach to the free energy of the warm dense electron gas and the uniform electron liquidTobias DornheimPanagiotis ToliasZhandos A. MoldabekovJan VorbergerWe explore the recently introduced η-ensemble approach to compute the free energy directly from ab initio path integral Monte Carlo (PIMC) simulations [T. Dornheim et al., Phys. Rev. B 111, L041114 (2025)2469-995010.1103/PhysRevB.111.L041114] and apply it to the archetypal uniform electron gas model both in the warm dense matter and strongly coupled regimes. Specifically, we present an in-depth study of the relevant algorithmic details such as the choice of the free weighting parameter and the choice of the optimum number of intermediate η-steps to connect the real, nonideal system (η=1) with the ideal limit (η=0). Moreover, we explore the inherent decomposition of the full free energy into its ideal bosonic, ideal-to-interacting, and bosonic-to-fermionic contributions for different parameter regimes. Finally, we compare our new free energy data with an existing free energy parametrization [Groth et al., Phys. Rev. Lett. 119, 135001 (2017)0031-900710.1103/PhysRevLett.119.135001] obtained via adiabatic connection formula evaluations, and we find very good agreement in its range of applicability, i.e., for density parameters r_{s}≤20; in addition, we present the first PIMC results for the free energy in the low density regime of 20<r_{s}≤100. We expect our results to be of interest both for the study of matter under extreme conditions, as well as to the more general field of PIMC simulations of interacting quantum many-body systems.http://doi.org/10.1103/4n7x-78fs
spellingShingle Tobias Dornheim
Panagiotis Tolias
Zhandos A. Moldabekov
Jan Vorberger
η-ensemble path integral Monte Carlo approach to the free energy of the warm dense electron gas and the uniform electron liquid
Physical Review Research
title η-ensemble path integral Monte Carlo approach to the free energy of the warm dense electron gas and the uniform electron liquid
title_full η-ensemble path integral Monte Carlo approach to the free energy of the warm dense electron gas and the uniform electron liquid
title_fullStr η-ensemble path integral Monte Carlo approach to the free energy of the warm dense electron gas and the uniform electron liquid
title_full_unstemmed η-ensemble path integral Monte Carlo approach to the free energy of the warm dense electron gas and the uniform electron liquid
title_short η-ensemble path integral Monte Carlo approach to the free energy of the warm dense electron gas and the uniform electron liquid
title_sort η ensemble path integral monte carlo approach to the free energy of the warm dense electron gas and the uniform electron liquid
url http://doi.org/10.1103/4n7x-78fs
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