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Akhmetov F, Vorberger J, Milov I, Makhotkin I, Ackermann M. Ab initio-simulated optical response of hot electrons in gold and ruthenium. OPTICS EXPRESS 2024; 32:19117-19132. [PMID: 38859054 DOI: 10.1364/oe.522772] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2024] [Accepted: 04/13/2024] [Indexed: 06/12/2024]
Abstract
Optical femtosecond pump-probe experiments allow to measure the dynamics of ultrafast heating of metals with high accuracy. However, the theoretical analysis of such experiments is often complicated because of the indirect connection of the measured signal and the desired temperature transients. Establishing such a connection requires an accurate model of the optical constants of a metal, depending on both the electron temperature Te and the lattice temperature Tl. In this paper, we present first-principles simulations of the two-temperature scenario with Te ≫ Tl, showing the optical response of hot electrons to laser irradiation in gold and ruthenium. Comparing our simulations with the Kubo-Greenwood approach, we discuss the influence of electron-phonon and electron-electron scattering on the intraband contribution to optical constants. Applying the simulated optical constants to the analysis of ultrafast heating of ruthenium thin films we highlight the importance of the latter scattering channel to understand the measured heating dynamics.
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Dornheim T, Schwalbe S, Moldabekov ZA, Vorberger J, Tolias P. Ab Initio Path Integral Monte Carlo Simulations of the Uniform Electron Gas on Large Length Scales. J Phys Chem Lett 2024; 15:1305-1313. [PMID: 38285536 PMCID: PMC10860150 DOI: 10.1021/acs.jpclett.3c03193] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Revised: 01/17/2024] [Accepted: 01/22/2024] [Indexed: 01/31/2024]
Abstract
The accurate description of non-ideal quantum many-body systems is of prime importance for a host of applications within physics, quantum chemistry, materials science, and related disciplines. At finite temperatures, the gold standard is given by ab initio path integral Monte Carlo (PIMC) simulations, which do not require any empirical input but exhibit an exponential increase in the required computation time for Fermionic systems with an increase in system size N. Very recently, computing Fermionic properties without this bottleneck based on PIMC simulations of fictitious identical particles has been suggested. In our work, we use this technique to perform very large (N ≤ 1000) PIMC simulations of the warm dense electron gas and demonstrate that it is capable of providing a highly accurate description of the investigated properties, i.e., the static structure factor, the static density response function, and the local field correction, over the entire range of length scales.
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Affiliation(s)
- Tobias Dornheim
- Center
for Advanced Systems Understanding (CASUS), Helmholtz-Zentrum Dresden-Rossendorf (HZDR), D-02826 Görlitz, Germany
| | - Sebastian Schwalbe
- Center
for Advanced Systems Understanding (CASUS), Helmholtz-Zentrum Dresden-Rossendorf (HZDR), D-02826 Görlitz, Germany
| | - Zhandos A. Moldabekov
- Center
for Advanced Systems Understanding (CASUS), Helmholtz-Zentrum Dresden-Rossendorf (HZDR), D-02826 Görlitz, Germany
| | - Jan Vorberger
- Institute
of Radiation Physics, Helmholtz-Zentrum
Dresden-Rossendorf (HZDR), D-01328 Dresden, Germany
| | - Panagiotis Tolias
- Space
and Plasma Physics, Royal Institute of Technology
(KTH), Stockholm SE-100 44, Sweden
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Schörner M, Bethkenhagen M, Döppner T, Kraus D, Fletcher LB, Glenzer SH, Redmer R. X-ray Thomson scattering spectra from density functional theory molecular dynamics simulations based on a modified Chihara formula. Phys Rev E 2023; 107:065207. [PMID: 37464593 DOI: 10.1103/physreve.107.065207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Accepted: 05/10/2023] [Indexed: 07/20/2023]
Abstract
We study ab initio approaches for calculating x-ray Thomson scattering spectra from density functional theory molecular dynamics simulations based on a modified Chihara formula that expresses the inelastic contribution in terms of the dielectric function. We study the electronic dynamic structure factor computed from the Mermin dielectric function using an ab initio electron-ion collision frequency in comparison to computations using a linear-response time-dependent density functional theory (LR-TDDFT) framework for hydrogen and beryllium and investigate the dispersion of free-free and bound-free contributions to the scattering signal. A separate treatment of these contributions, where only the free-free part follows the Mermin dispersion, shows good agreement with LR-TDDFT results for ambient-density beryllium, but breaks down for highly compressed matter where the bound states become pressure ionized. LR-TDDFT is used to reanalyze x-ray Thomson scattering experiments on beryllium demonstrating strong deviations from the plasma conditions inferred with traditional analytic models at small scattering angles.
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Affiliation(s)
| | - Mandy Bethkenhagen
- École Normale Supérieure de Lyon, Laboratoire de Géologie de Lyon, CNRS UMR 5276, 69364 Lyon, Cedex 07, France
- Institute of Science and Technology Austria, Am Campus 1, 3400 Klosterneuburg, Austria
| | - Tilo Döppner
- Lawrence Livermore National Laboratory, Livermore, California 94551, USA
| | - Dominik Kraus
- University of Rostock, Institute of Physics, 18051 Rostock, Germany
- Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany
| | - Luke B Fletcher
- SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | | | - Ronald Redmer
- University of Rostock, Institute of Physics, 18051 Rostock, Germany
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Fedorov ID, Stegailov VV. Exciton Nature of Plasma Phase Transition in Warm Dense Fluid Hydrogen: ROKS Simulation. Chemphyschem 2023; 24:e202200730. [PMID: 36399362 DOI: 10.1002/cphc.202200730] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Revised: 11/16/2022] [Accepted: 11/18/2022] [Indexed: 11/19/2022]
Abstract
The transition of warm dense fluid hydrogen from an insulator to a conducting state at pressures of about 20-400 GPa and temperatures of 500-5000 K has been the subject of active scientific research over the past few decades. However, various experimental and theoretical methods do not provide consistent results. In this work, we have applied the restricted open-shell Kohn-Sham (ROKS) method for first principles molecular dynamics of dense hydrogen after thermal excitation to the first singlet excited state. The Wannier localization method has allowed us to analyze the exciton dynamics in this system. The model shows that a key mechanism of the transition is associated with the dissociation of electron-hole pairs, which allows explaining several stages of the transition of fluid H2 from molecular state to plasma. This mechanism is able to give a quantitative description of several experimental results as well as to resolve the discrepancies between experimental studies.
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Affiliation(s)
- Ilya D Fedorov
- Joint Institute for High Temperatures of Russian Academy of Sciences, Izhorskaya st. 13-2, Moscow, 125412, Russia.,Moscow Institute of Physics and Technologies, National Research University), Institutskij per. 9, Dolgoprudny, Moscow, 141700, Russia.,National Research University Higher School of Economics, Myasnitskaya Ulitsa 20, Moscow, 101000, Russia
| | - Vladimir V Stegailov
- Joint Institute for High Temperatures of Russian Academy of Sciences, Izhorskaya st. 13-2, Moscow, 125412, Russia.,Moscow Institute of Physics and Technologies, National Research University), Institutskij per. 9, Dolgoprudny, Moscow, 141700, Russia.,National Research University Higher School of Economics, Myasnitskaya Ulitsa 20, Moscow, 101000, Russia
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French M, Röpke G, Schörner M, Bethkenhagen M, Desjarlais MP, Redmer R. Electronic transport coefficients from density functional theory across the plasma plane. Phys Rev E 2022; 105:065204. [PMID: 35854489 DOI: 10.1103/physreve.105.065204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Accepted: 05/18/2022] [Indexed: 06/15/2023]
Abstract
We investigate the thermopower and Lorenz number of hydrogen with Kohn-Sham density functional theory (DFT) across the plasma plane toward the near-classical limit, i.e., weakly degenerate and weakly coupled states. Our results are in concordance with certain limiting values for the Lorentz plasma, a model system which only considers electron-ion scattering. Thereby, we clearly show that the widely used method of calculating transport properties via the Kubo-Greenwood (KG) formalism does not capture electron-electron scattering processes. Our discussion also addresses the inadequateness of assuming a Drude-like frequency behavior for the conductivity of nondegenerate plasmas by revisiting the relaxation time approximation within kinetic theory.
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Affiliation(s)
- Martin French
- Universität Rostock, Institut für Physik, Albert-Einstein-Str. 23-24, D-18059 Rostock, Germany
| | - Gerd Röpke
- Universität Rostock, Institut für Physik, Albert-Einstein-Str. 23-24, D-18059 Rostock, Germany
| | - Maximilian Schörner
- Universität Rostock, Institut für Physik, Albert-Einstein-Str. 23-24, D-18059 Rostock, Germany
| | - Mandy Bethkenhagen
- Universität Rostock, Institut für Physik, Albert-Einstein-Str. 23-24, D-18059 Rostock, Germany
- École Normale Supérieure de Lyon, Université Lyon 1, Laboratoire de Géologie de Lyon, CNRS UMR 5276, 69364 Lyon Cedex 07, France
| | | | - Ronald Redmer
- Universität Rostock, Institut für Physik, Albert-Einstein-Str. 23-24, D-18059 Rostock, Germany
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