1
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Moldabekov Z, Schwalbe S, Böhme MP, Vorberger J, Shao X, Pavanello M, Graziani FR, Dornheim T. Bound-State Breaking and the Importance of Thermal Exchange-Correlation Effects in Warm Dense Hydrogen. J Chem Theory Comput 2024; 20:68-78. [PMID: 38133546 PMCID: PMC10782774 DOI: 10.1021/acs.jctc.3c00934] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Revised: 12/01/2023] [Accepted: 12/01/2023] [Indexed: 12/23/2023]
Abstract
Hydrogen at extreme temperatures and pressures is of key relevance for cutting-edge technological applications, with inertial confinement fusion research being a prime example. In addition, it is ubiquitous throughout our universe and naturally occurs in a variety of astrophysical objects. In the present work, we present exact ab initio path integral Monte Carlo (PIMC) results for the electronic density of warm dense hydrogen along a line of constant degeneracy across a broad range of densities. Using the well-known concept of reduced density gradients, we develop a new framework to identify the breaking of bound states due to pressure ionization in bulk hydrogen. Moreover, we use our PIMC results as a reference to rigorously assess the accuracy of a variety of exchange-correlation (XC) functionals in density functional theory calculations for different density regions. Here, a key finding is the importance of thermal XC effects for the accurate description of density gradients in high-energy-density systems. Our exact PIMC test set is freely available online and can be used to guide the development of new methodologies for the simulation of warm dense matter and beyond.
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Affiliation(s)
- Zhandos Moldabekov
- Center
for Advanced Systems Understanding (CASUS), Görlitz D-02826, Germany
- Helmholtz-Zentrum
Dresden-Rossendorf (HZDR), Dresden D-01328, Germany
| | - Sebastian Schwalbe
- Center
for Advanced Systems Understanding (CASUS), Görlitz D-02826, Germany
- Helmholtz-Zentrum
Dresden-Rossendorf (HZDR), Dresden D-01328, Germany
| | | | - Jan Vorberger
- Helmholtz-Zentrum
Dresden-Rossendorf (HZDR), Dresden D-01328, Germany
| | - Xuecheng Shao
- Department
of Chemistry, Rutgers University, Newark, New Jersey 07102, United States
- Department
of Physics, Rutgers University, Newark, New Jersey 07102, United States
| | - Michele Pavanello
- Department
of Chemistry, Rutgers University, Newark, New Jersey 07102, United States
- Department
of Physics, Rutgers University, Newark, New Jersey 07102, United States
| | - Frank R. Graziani
- Lawrence
Livermore National Laboratory (LLNL), Livermore 94550, California, United States
| | - Tobias Dornheim
- Center
for Advanced Systems Understanding (CASUS), Görlitz D-02826, Germany
- Helmholtz-Zentrum
Dresden-Rossendorf (HZDR), Dresden D-01328, Germany
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2
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Xie H, Li ZH, Wang H, Zhang L, Wang L. Deep Variational Free Energy Approach to Dense Hydrogen. PHYSICAL REVIEW LETTERS 2023; 131:126501. [PMID: 37802941 DOI: 10.1103/physrevlett.131.126501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 08/01/2023] [Accepted: 08/14/2023] [Indexed: 10/08/2023]
Abstract
We developed a deep generative model-based variational free energy approach to the equations of state of dense hydrogen. We employ a normalizing flow network to model the proton Boltzmann distribution and a fermionic neural network to model the electron wave function at given proton positions. By jointly optimizing the two neural networks we reached a comparable variational free energy to the previous coupled electron-ion Monte Carlo calculation. The predicted equation of state of dense hydrogen under planetary conditions is denser than the findings of ab initio molecular dynamics calculation and empirical chemical model. Moreover, direct access to the entropy and free energy of dense hydrogen opens new opportunities in planetary modeling and high-pressure physics research.
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Affiliation(s)
- Hao Xie
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Zi-Hang Li
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Han Wang
- Laboratory of Computational Physics, Institute of Applied Physics and Computational Mathematics, Fenghao East Road 2, Beijing 100094, China
| | - Linfeng Zhang
- DP Technology, Beijing 100080, China
- AI for Science Institute, Beijing 100080, China
| | - Lei Wang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
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3
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Dornheim T, Böhme MP, Moldabekov ZA, Vorberger J. Electronic density response of warm dense hydrogen on the nanoscale. Phys Rev E 2023; 108:035204. [PMID: 37849144 DOI: 10.1103/physreve.108.035204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Accepted: 08/11/2023] [Indexed: 10/19/2023]
Abstract
The properties of hydrogen at warm dense matter (WDM) conditions are of high importance for the understanding of astrophysical objects and technological applications such as inertial confinement fusion. In this work, we present extensive ab initio path integral Monte Carlo results for the electronic properties in the Coulomb potential of a fixed ionic configuration. This gives us unique insights into the complex interplay between the electronic localization around the protons with their density response to an external harmonic perturbation. We find qualitative agreement between our simulation data and a heuristic model based on the assumption of a local uniform electron gas model, but important trends are not captured by this simplification. In addition to being interesting in their own right, we are convinced that our results will be of high value for future projects, such as the rigorous benchmarking of approximate theories for the simulation of WDM, most notably density functional theory.
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Affiliation(s)
- Tobias Dornheim
- Center for Advanced Systems Understanding (CASUS), D-02826 Görlitz, Germany
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), D-01328 Dresden, Germany
| | - Maximilian P Böhme
- Center for Advanced Systems Understanding (CASUS), D-02826 Görlitz, Germany
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), D-01328 Dresden, Germany
- Technische Universität Dresden, D-01062 Dresden, Germany
| | - Zhandos A Moldabekov
- Center for Advanced Systems Understanding (CASUS), D-02826 Görlitz, Germany
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), D-01328 Dresden, Germany
| | - Jan Vorberger
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), D-01328 Dresden, Germany
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4
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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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5
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Niu H, Yang Y, Jensen S, Holzmann M, Pierleoni C, Ceperley DM. Stable Solid Molecular Hydrogen above 900 K from a Machine-Learned Potential Trained with Diffusion Quantum Monte Carlo. PHYSICAL REVIEW LETTERS 2023; 130:076102. [PMID: 36867819 DOI: 10.1103/physrevlett.130.076102] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 11/29/2022] [Accepted: 01/12/2023] [Indexed: 06/18/2023]
Abstract
We survey the phase diagram of high-pressure molecular hydrogen with path integral molecular dynamics using a machine-learned interatomic potential trained with quantum Monte Carlo forces and energies. Besides the HCP and C2/c-24 phases, we find two new stable phases both with molecular centers in the Fmmm-4 structure, separated by a molecular orientation transition with temperature. The high temperature isotropic Fmmm-4 phase has a reentrant melting line with a maximum at higher temperature (1450 K at 150 GPa) than previously estimated and crosses the liquid-liquid transition line around 1200 K and 200 GPa.
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Affiliation(s)
- Hongwei Niu
- Department of Astronautical Science and Mechanics, Harbin Institute of Technology, Harbin, Heilongjiang 150001, China
| | - Yubo Yang
- Center for Computational Quantum Physics, Flatiron Institute, New York, New York 10010, USA
- Department of Physics, University of Illinois, Urbana, Illinois 61801, USA
| | - Scott Jensen
- Department of Physics, University of Illinois, Urbana, Illinois 61801, USA
| | | | - Carlo Pierleoni
- Department of Physical and Chemical Sciences, University of L'Aquila, Via Vetoio 10, I-67010 L'Aquila, Italy
| | - David M Ceperley
- Department of Physics, University of Illinois, Urbana, Illinois 61801, USA
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6
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Moldabekov Z, Böhme M, Vorberger J, Blaschke D, Dornheim T. Ab Initio Static Exchange-Correlation Kernel across Jacob's Ladder without Functional Derivatives. J Chem Theory Comput 2023; 19:1286-1299. [PMID: 36724889 PMCID: PMC9979610 DOI: 10.1021/acs.jctc.2c01180] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The electronic exchange─correlation (XC) kernel constitutes a fundamental input for the estimation of a gamut of properties such as the dielectric characteristics, the thermal and electrical conductivity, or the response to an external perturbation. In this work, we present a formally exact methodology for the computation of the system specific static XC kernel exclusively within the framework of density functional theory (DFT) and without employing functional derivatives─no external input apart from the usual XC-functional is required. We compare our new results with exact quantum Monte Carlo (QMC) data for the archetypical uniform electron gas model under both ambient and warm dense matter conditions. This gives us unprecedented insights into the performance of different XC functionals, and it has important implications for the development of new functionals that are designed for the application at extreme temperatures. In addition, we obtain new DFT results for the XC kernel of warm dense hydrogen as it occurs in fusion applications and astrophysical objects. The observed excellent agreement to the QMC reference data demonstrates that presented framework is capable to capture nontrivial effects such as XC-induced isotropy breaking in the density response of hydrogen at large wave numbers.
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Affiliation(s)
- Zhandos Moldabekov
- Center
for Advanced Systems Understanding (CASUS), D-02826Görlitz, Germany,Helmholtz-Zentrum
Dresden-Rossendorf (HZDR), D-01328Dresden, Germany,E-mail:
| | - Maximilian Böhme
- Center
for Advanced Systems Understanding (CASUS), D-02826Görlitz, Germany
| | - Jan Vorberger
- Helmholtz-Zentrum
Dresden-Rossendorf (HZDR), D-01328Dresden, Germany
| | - David Blaschke
- Institute
of Theoretical Physics, University of Wroclaw, 50-204Wroclaw, Poland
| | - Tobias Dornheim
- Center
for Advanced Systems Understanding (CASUS), D-02826Görlitz, Germany,Helmholtz-Zentrum
Dresden-Rossendorf (HZDR), D-01328Dresden, Germany,E-mail:
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7
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Böhme M, Moldabekov ZA, Vorberger J, Dornheim T. Ab initio path integral Monte Carlo simulations of hydrogen snapshots at warm dense matter conditions. Phys Rev E 2023; 107:015206. [PMID: 36797933 DOI: 10.1103/physreve.107.015206] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Accepted: 12/19/2022] [Indexed: 06/18/2023]
Abstract
We combine ab initio path integral Monte Carlo (PIMC) simulations with fixed ion configurations from density functional theory molecular dynamics (DFT-MD) simulations to solve the electronic problem for hydrogen under warm dense matter conditions [Böhme et al., Phys. Rev. Lett. 129, 066402 (2022)0031-900710.1103/PhysRevLett.129.066402]. The problem of path collapse due to the Coulomb attraction is avoided by utilizing the pair approximation, which is compared against the simpler Kelbg pair potential. We find very favorable convergence behavior towards the former. Since we do not impose any nodal restrictions, our PIMC simulations are afflicted with the notorious fermion sign problem, which we analyze in detail. While computationally demanding, our results constitute an exact benchmark for other methods and approximations within DFT. Our setup gives us the unique capability to study important properties of warm dense hydrogen such as the electronic static density response and exchange-correlation kernel without any model assumptions, which will be very valuable for a variety of applications such as the interpretation of experiments and the development of new XC functionals.
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Affiliation(s)
- Maximilian Böhme
- Center for Advanced Systems Understanding (CASUS), D-02826 Görlitz, Germany
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Institute of Radiation Physics, D-01328 Dresden, Germany
- Technische Universität Dresden, Institute of Theoretical Physics, D-01062 Dresden, Germany
| | - Zhandos A Moldabekov
- Center for Advanced Systems Understanding (CASUS), D-02826 Görlitz, Germany
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Institute of Radiation Physics, D-01328 Dresden, Germany
| | - Jan Vorberger
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Institute of Radiation Physics, D-01328 Dresden, Germany
| | - Tobias Dornheim
- Center for Advanced Systems Understanding (CASUS), D-02826 Görlitz, Germany
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Institute of Radiation Physics, D-01328 Dresden, Germany
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8
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Zhou Y, Lopez GE, Giovambattista N. Anomalous properties in the potential energy landscape of a monatomic liquid across the liquid-gas and liquid-liquid phase transitions. J Chem Phys 2022; 157:124502. [PMID: 36182441 PMCID: PMC9525132 DOI: 10.1063/5.0106923] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Accepted: 08/26/2022] [Indexed: 11/14/2022] Open
Abstract
As a liquid approaches the gas state, the properties of the potential energy landscape (PEL) sampled by the system become anomalous. Specifically, (i) the mechanically stable local minima of the PEL [inherent structures (IS)] can exhibit cavitation above the so-called Sastry volume, vS, before the liquid enters the gas phase. In addition, (ii) the pressure of the liquid at the sampled IS [i.e., the PEL equation of state, PIS(v)] develops a spinodal-like minimum at vS. We perform molecular dynamics simulations of a monatomic water-like liquid and verify that points (i) and (ii) hold at high temperatures. However, at low temperatures, cavitation in the liquid and the corresponding IS occurs simultaneously and a Sastry volume cannot be defined. Remarkably, at intermediate/high temperatures, the IS of the liquid can exhibit crystallization, i.e., the liquid regularly visits the regions of the PEL that belong to the crystal state. The model liquid considered also exhibits a liquid-liquid phase transition (LLPT) between a low-density and a high-density liquid (LDL and HDL). By studying the behavior of PIS(v) during the LLPT, we identify a Sastry volume for both LDL and HDL. The HDL Sastry volume marks the onset above which IS are heterogeneous (composed of LDL and HDL particles), analogous to points (i) and (ii) above. However, the relationship between the LDL Sastry volume and the onset of heterogeneous IS is less evident. We conclude by presenting a thermodynamic argument that can explain the behavior of the PEL equation of state PIS(v) across both the liquid-gas phase transition and LLPT.
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9
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Fried NR, Longo TJ, Anisimov MA. Thermodynamic modeling of fluid polyamorphism in hydrogen at extreme conditions. J Chem Phys 2022; 157:101101. [DOI: 10.1063/5.0107043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Fluid polyamorphism, the existence of multiple amorphous fluid states in a single-component system, has been observed or predicted in a variety of substances. A remarkable example of this phenomenon is the fluid–fluid phase transition (FFPT) in high-pressure hydrogen between insulating and conducting high-density fluids. This transition is induced by the reversible dimerization/dissociation of the molecular and atomistic states of hydrogen. In this work, we present the first attempt to thermodynamically model the FFPT in hydrogen at extreme conditions. Our predictions for the phase coexistence and the reaction equilibrium of the two alternative forms of fluid hydrogen are based on experimental data and supported by the results of simulations. Remarkably, we find that the law of corresponding states can be utilized to construct a unified equation of state combining the available computational results for different models of hydrogen and the experimental data.
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Affiliation(s)
- Nathaniel R. Fried
- Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA
| | - Thomas J. Longo
- Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA
| | - Mikhail A. Anisimov
- Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA
- Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, Maryland 20742, USA
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10
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Böhme M, Moldabekov ZA, Vorberger J, Dornheim T. Static Electronic Density Response of Warm Dense Hydrogen: Ab Initio Path Integral Monte Carlo Simulations. PHYSICAL REVIEW LETTERS 2022; 129:066402. [PMID: 36018668 DOI: 10.1103/physrevlett.129.066402] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 05/12/2022] [Accepted: 06/23/2022] [Indexed: 06/15/2023]
Abstract
The properties of hydrogen under extreme conditions are important for many applications, including inertial confinement fusion and astrophysical models. A key quantity is given by the electronic density response to an external perturbation, which is probed in x-ray Thomson scattering experiments-the state of the art diagnostics from which system parameters like the free electron density n_{e}, the electronic temperature T_{e}, and the charge state Z can be inferred. In this work, we present highly accurate path integral Monte Carlo results for the static electronic density response of hydrogen. We obtain the static exchange-correlation (XC) kernel K_{XC}, which is of central relevance for many applications, such as time-dependent density functional theory. This gives us a first unbiased look into the electronic density response of hydrogen in the warm-dense matter regime, thereby opening up a gamut of avenues for future research.
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Affiliation(s)
- Maximilian Böhme
- Center for Advanced Systems Understanding (CASUS), D-02826 Görlitz, Germany
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), D-01328 Dresden, Germany
- Technische Universität Dresden, D-01062 Dresden, Germany
| | - Zhandos A Moldabekov
- Center for Advanced Systems Understanding (CASUS), D-02826 Görlitz, Germany
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), D-01328 Dresden, Germany
| | - Jan Vorberger
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), D-01328 Dresden, Germany
| | - Tobias Dornheim
- Center for Advanced Systems Understanding (CASUS), D-02826 Görlitz, Germany
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), D-01328 Dresden, Germany
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11
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Shumovskyi NA, Longo TJ, Buldyrev SV, Anisimov MA. Modeling fluid polyamorphism through a maximum-valence approach. Phys Rev E 2022; 106:015305. [PMID: 35974620 DOI: 10.1103/physreve.106.015305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Accepted: 06/07/2022] [Indexed: 06/15/2023]
Abstract
We suggest a simple model to describe polyamorphism in single-component fluids using a maximum-valence approach. The model contains three types of interactions: (i) Atoms attract each other by van der Waals forces that generate a liquid-gas transition at low pressures, (ii) atoms may form covalent bonds that induce association, and (iii) atoms with maximal valence attract or repel each other stronger than other atoms, thus generating liquid-liquid separation. As an example, we qualitatively compare this model with the behavior of liquid sulfur and show that condition (iii) generates a liquid-liquid phase transition in addition to the liquid-gas phase transition.
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Affiliation(s)
| | - Thomas J Longo
- Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA
| | - Sergey V Buldyrev
- Department of Physics, Yeshiva University, New York, New York 10033, USA and Department of Physics, Boston University, Massachusetts 02215, USA
| | - Mikhail A Anisimov
- Department of Chemical and Biomolecular Engineering and Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA
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12
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Martí J, Mazzanti F, Astrakharchik GE, Batet L, Portos-Amill L, Pedreño B. Nucleation of Helium in Liquid Lithium at 843 K and High Pressures. MATERIALS 2022; 15:ma15082866. [PMID: 35454558 PMCID: PMC9030494 DOI: 10.3390/ma15082866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Revised: 04/08/2022] [Accepted: 04/12/2022] [Indexed: 11/24/2022]
Abstract
Fusion energy stands out as a promising alternative for a future decarbonised energy system. In order to be sustainable, future fusion nuclear reactors will have to produce their own tritium. In the so-called breeding blanket of a reactor, the neutron bombardment of lithium will produce the desired tritium, but also helium, which can trigger nucleation mechanisms owing to the very low solubility of helium in liquid metals. An understanding of the underlying microscopic processes is important for improving the efficiency, sustainability and reliability of the fusion energy conversion process. The spontaneous creation of helium droplets or bubbles in the liquid metal used as breeding material in some designs may be a serious issue for the performance of the breeding blankets. This phenomenon has yet to be fully studied and understood. This work aims to provide some insight on the behaviour of lithium and helium mixtures at experimentally corresponding operating conditions (843 K and pressures between 108 and 1010 Pa). We report a microscopic study of the thermodynamic, structural and dynamical properties of lithium–helium mixtures, as a first step to the simulation of the environment in a nuclear fusion power plant. We introduce a new microscopic model devised to describe the formation of helium droplets in the thermodynamic range considered. Our model predicts the formation of helium droplets at pressures around 109 Pa, with radii between 1 and 2 Å. The diffusion coefficient of lithium (2 Å2/ps) is in excellent agreement with reference experimental data, whereas the diffusion coefficient of helium is in the range of 1 Å2/ps and tends to decrease as pressure increases.
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Affiliation(s)
- Jordi Martí
- Department of Physics, Polytechnic University of Catalonia-Barcelona Tech, 08034 Barcelona, Spain; (F.M.); (G.E.A.); (L.B.)
- Correspondence:
| | - Ferran Mazzanti
- Department of Physics, Polytechnic University of Catalonia-Barcelona Tech, 08034 Barcelona, Spain; (F.M.); (G.E.A.); (L.B.)
| | - Grigori E. Astrakharchik
- Department of Physics, Polytechnic University of Catalonia-Barcelona Tech, 08034 Barcelona, Spain; (F.M.); (G.E.A.); (L.B.)
| | - Lluís Batet
- Department of Physics, Polytechnic University of Catalonia-Barcelona Tech, 08034 Barcelona, Spain; (F.M.); (G.E.A.); (L.B.)
| | - Laura Portos-Amill
- Barcelona School of Telecommunications Engineering, Polytechnic University of Catalonia-Barcelona Tech, 08034 Barcelona, Spain; (L.P.-A.); (B.P.)
| | - Borja Pedreño
- Barcelona School of Telecommunications Engineering, Polytechnic University of Catalonia-Barcelona Tech, 08034 Barcelona, Spain; (L.P.-A.); (B.P.)
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13
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Boeri L, Hennig R, Hirschfeld P, Profeta G, Sanna A, Zurek E, Pickett WE, Amsler M, Dias R, Eremets MI, Heil C, Hemley RJ, Liu H, Ma Y, Pierleoni C, Kolmogorov AN, Rybin N, Novoselov D, Anisimov V, Oganov AR, Pickard CJ, Bi T, Arita R, Errea I, Pellegrini C, Requist R, Gross EKU, Margine ER, Xie SR, Quan Y, Hire A, Fanfarillo L, Stewart GR, Hamlin JJ, Stanev V, Gonnelli RS, Piatti E, Romanin D, Daghero D, Valenti R. The 2021 room-temperature superconductivity roadmap. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:183002. [PMID: 34544070 DOI: 10.1088/1361-648x/ac2864] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Accepted: 09/20/2021] [Indexed: 06/13/2023]
Abstract
Designing materials with advanced functionalities is the main focus of contemporary solid-state physics and chemistry. Research efforts worldwide are funneled into a few high-end goals, one of the oldest, and most fascinating of which is the search for an ambient temperature superconductor (A-SC). The reason is clear: superconductivity at ambient conditions implies being able to handle, measure and access a single, coherent, macroscopic quantum mechanical state without the limitations associated with cryogenics and pressurization. This would not only open exciting avenues for fundamental research, but also pave the road for a wide range of technological applications, affecting strategic areas such as energy conservation and climate change. In this roadmap we have collected contributions from many of the main actors working on superconductivity, and asked them to share their personal viewpoint on the field. The hope is that this article will serve not only as an instantaneous picture of the status of research, but also as a true roadmap defining the main long-term theoretical and experimental challenges that lie ahead. Interestingly, although the current research in superconductor design is dominated by conventional (phonon-mediated) superconductors, there seems to be a widespread consensus that achieving A-SC may require different pairing mechanisms.In memoriam, to Neil Ashcroft, who inspired us all.
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Affiliation(s)
- Lilia Boeri
- Physics Department, Sapienza University and Enrico Fermi Research Center, Rome, Italy
| | - Richard Hennig
- Deparment of Material Science and Engineering and Quantum Theory Project, University of Florida, Gainesville 32611, United States of America
| | - Peter Hirschfeld
- Department of Physics, University of Florida, Gainesville, FL 32611, United States of America
| | | | - Antonio Sanna
- Max Planck Institute of Microstructure Physics, Halle, Germany
| | - Eva Zurek
- University at Buffalo, SUNY, United States of America
| | | | - Maximilian Amsler
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
- Department of Materials Science and Engineering, Cornell University, Ithaca, NY 14853, United States of America
| | - Ranga Dias
- University of Rochester, United States of America
| | | | | | | | - Hanyu Liu
- Jilin University, People's Republic of China
| | - Yanming Ma
- Jilin University, People's Republic of China
| | - Carlo Pierleoni
- Department of Physics, University of Florida, Gainesville, FL 32611, United States of America
| | | | | | | | | | | | | | - Tiange Bi
- University at Buffalo, SUNY, United States of America
| | | | - Ion Errea
- University of the Basque Country, Spain
| | | | - Ryan Requist
- Max Planck Institute of Microstructure Physics, Halle, Germany
- Hebrew University of Jerusalem, Israel
| | - E K U Gross
- Max Planck Institute of Microstructure Physics, Halle, Germany
- Hebrew University of Jerusalem, Israel
| | | | - Stephen R Xie
- Department of Physics, University of Florida, Gainesville, FL 32611, United States of America
| | - Yundi Quan
- Department of Physics, University of Florida, Gainesville, FL 32611, United States of America
| | - Ajinkya Hire
- Department of Physics, University of Florida, Gainesville, FL 32611, United States of America
| | - Laura Fanfarillo
- Department of Physics, University of Florida, Gainesville, FL 32611, United States of America
- Scuola Internazionale Superiore di Studi Avanzati (SISSA), Via Bonomea 265, 34136 Trieste, Italy
| | - G R Stewart
- Department of Physics, University of Florida, Gainesville, FL 32611, United States of America
| | - J J Hamlin
- Department of Physics, University of Florida, Gainesville, FL 32611, United States of America
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14
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Karasiev VV, Hinz J, Hu SX, Trickey SB. On the liquid-liquid phase transition of dense hydrogen. Nature 2021; 600:E12-E14. [PMID: 34912080 DOI: 10.1038/s41586-021-04078-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2020] [Accepted: 09/30/2021] [Indexed: 11/09/2022]
Affiliation(s)
- Valentin V Karasiev
- Laboratory for Laser Energetics, University of Rochester, Rochester, NY, USA.
| | - Joshua Hinz
- Laboratory for Laser Energetics, University of Rochester, Rochester, NY, USA
| | - S X Hu
- Laboratory for Laser Energetics, University of Rochester, Rochester, NY, USA
| | - S B Trickey
- Quantum Theory Project, Department of Physics, University of Florida, Gainesville, FL, USA
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15
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van de Bund S, Wiebe H, Ackland GJ. Isotope Quantum Effects in the Metallization Transition in Liquid Hydrogen. PHYSICAL REVIEW LETTERS 2021; 126:225701. [PMID: 34152180 DOI: 10.1103/physrevlett.126.225701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2020] [Revised: 11/12/2020] [Accepted: 04/21/2021] [Indexed: 06/13/2023]
Abstract
Quantum effects in condensed matter normally only occur at low temperatures. Here we show a large quantum effect in high-pressure liquid hydrogen at thousands of Kelvins. We show that the metallization transition in hydrogen is subject to a very large isotope effect, occurring hundreds of degrees lower than the equivalent transition in deuterium. We examined this using path integral molecular dynamics simulations which identify a liquid-liquid transition involving atomization, metallization, and changes in viscosity, specific heat, and compressibility. The difference between H_{2} and D_{2} is a quantum mechanical effect that can be associated with the larger zero-point energy in H_{2} weakening the covalent bond. Our results mean that experimental results on deuterium must be corrected before they are relevant to understanding hydrogen at planetary conditions.
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Affiliation(s)
- Sebastiaan van de Bund
- School of Physics & Astronomy, The University of Edinburgh, Edinburgh EH9 3FD, United Kingdom
| | - Heather Wiebe
- School of Physics & Astronomy, The University of Edinburgh, Edinburgh EH9 3FD, United Kingdom
| | - Graeme J Ackland
- School of Physics & Astronomy, The University of Edinburgh, Edinburgh EH9 3FD, United Kingdom
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16
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Tian C, Liu F, Yuan H, Chen H, Gan Y. First-principles equation of state of liquid hydrogen and dissociative transition. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:015401. [PMID: 32932242 DOI: 10.1088/1361-648x/abb896] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The properties of dense hot hydrogen, in particular the phase transition between the molecular insulating and atomic conductive states, are important in the fields of astrophysics and high-pressure physics. Previous ab initio calculations suggested the metallization in liquid hydrogen, accompanied by dissociation, is a first-order phase transition and ends at a critical point in temperature range between 1500 and 2000 K and pressure close to 100 GPa. Using density functional theoretical molecular dynamics simulations, we report a first-principles equation of state of hydrogen that covers dissociation transition conditions at densities ranging from 0.20 to 1.00 g/cc and temperatures of 600-9000 K. Our results clearly indicate that a drop in pressure and a sharp structural change still occur as the system transforms from a diatomic to monoatomic phase at temperatures above 2000 K, and support the first-order phase transition in liquid hydrogen would end in the temperature about 4500 K.
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Affiliation(s)
- Chunling Tian
- School of Physical Science and Technology, Southwest University, Chongqing 400715, People's Republic of China
| | - Fusheng Liu
- Institute of High Pressure Physics, Southwest Jiaotong University, Chengdu 610031, People's Republic of China
| | - Hongkuan Yuan
- School of Physical Science and Technology, Southwest University, Chongqing 400715, People's Republic of China
| | - Hong Chen
- School of Physical Science and Technology, Southwest University, Chongqing 400715, People's Republic of China
| | - Yundan Gan
- Xi'an institute of modern chemistry, Xian 710000, People's Republic of China
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17
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Silvera IF, Dias R. Phases of the hydrogen isotopes under pressure: metallic hydrogen. ADVANCES IN PHYSICS: X 2021. [DOI: 10.1080/23746149.2021.1961607] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Affiliation(s)
| | - Ranga Dias
- Department of Physics and Astronomy and Mechanical Engineering, University of Rochester, Rochester, USA
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18
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Gorelov V, Ceperley DM, Holzmann M, Pierleoni C. Electronic structure and optical properties of quantum crystals from first principles calculations in the Born–Oppenheimer approximation. J Chem Phys 2020; 153:234117. [DOI: 10.1063/5.0031843] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Vitaly Gorelov
- Maison de la Simulation, CEA, CNRS, Univ. Paris-Sud, UVSQ, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
| | - David M. Ceperley
- Department of Physics, University of Illinois, Urbana, Illinois 61801, USA
| | - Markus Holzmann
- Univ. Grenoble Alpes, CNRS, LPMMC, 3800 Grenoble, France
- Institut Laue Langevin, BP 156, F-38042 Grenoble Cedex 9, France
| | - Carlo Pierleoni
- Maison de la Simulation, CEA, CNRS, Univ. Paris-Sud, UVSQ, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
- Department of Physical and Chemical Sciences, University of L’Aquila, Via Vetoio 10, I-67010 L’Aquila, Italy
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19
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Affiliation(s)
- Hajime Tanaka
- Department of Fundamental Engineering, Institute of Industrial Science, University of Tokyo, Meguro-ku, Tokyo 153-8505, Japan
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20
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Remsing RC, Klein ML. Molecular Simulation of Covalent Bond Dynamics in Liquid Silicon. J Phys Chem B 2020; 124:3180-3185. [PMID: 32216375 DOI: 10.1021/acs.jpcb.0c01798] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Many atomic liquids can form transient covalent bonds reminiscent of those in the corresponding solid states. These directional interactions dictate many important properties of the liquid state, necessitating a quantitative, atomic-scale understanding of bonding in these complex systems. A prototypical example is liquid silicon, wherein transient covalent bonds give rise to local tetrahedral order and consequent nontrivial effects on liquid-state thermodynamics and dynamics. To further understand covalent bonding in liquid silicon, and similar liquids, we present an ab initio-simulation-based approach for quantifying the structure and dynamics of covalent bonds in condensed phases. Through the examination of structural correlations among silicon nuclei and maximally localized Wannier function centers, we develop a geometric criterion for covalent bonds in liquid Si. We use this to monitor the dynamics of transient covalent bonding in the liquid state and estimate a covalent bond lifetime. We compare covalent bond dynamics to other processes in liquid Si and similar liquids and suggest experiments to measure the covalent bond lifetime.
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Affiliation(s)
- Richard C Remsing
- Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey 08854, United States
| | - Michael L Klein
- Institute for Computational Molecular Science and Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, United States
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21
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Gorelov V, Holzmann M, Ceperley DM, Pierleoni C. Energy Gap Closure of Crystalline Molecular Hydrogen with Pressure. PHYSICAL REVIEW LETTERS 2020; 124:116401. [PMID: 32242714 DOI: 10.1103/physrevlett.124.116401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Accepted: 02/13/2020] [Indexed: 06/11/2023]
Abstract
We study the gap closure with pressure of crystalline molecular hydrogen. The gaps are obtained from grand-canonical quantum Monte Carlo methods properly extended to quantum and thermal crystals, simulated by coupled electron ion Monte Carlo methods. Nuclear zero point effects cause a large reduction in the gap (∼2 eV). Depending on the structure, the fundamental indirect gap closes between 380 and 530 GPa for ideal crystals and 330-380 GPa for quantum crystals. Beyond this pressure the system enters into a bad metal phase where the density of states at the Fermi level increases with pressure up to ∼450-500 GPa when the direct gap closes. Our work partially supports the interpretation of recent experiments in high pressure hydrogen.
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Affiliation(s)
- Vitaly Gorelov
- Université Paris-Saclay, UVSQ, CNRS, CEA, Maison de la Simulation, 91191, Gif-sur-Yvette, France
| | - Markus Holzmann
- Univ. Grenoble Alpes, CNRS, LPMMC, 38000 Grenoble, France
- Institut Laue-Langevin, BP 156, F-38042 Grenoble Cedex 9, France
| | - David M Ceperley
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Carlo Pierleoni
- Université Paris-Saclay, UVSQ, CNRS, CEA, Maison de la Simulation, 91191, Gif-sur-Yvette, France
- Department of Physical and Chemical Sciences, University of L'Aquila, Via Vetoio 10, I-67010 L'Aquila, Italy
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22
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Jiang S, Holtgrewe N, Geballe ZM, Lobanov SS, Mahmood MF, McWilliams RS, Goncharov AF. A Spectroscopic Study of the Insulator-Metal Transition in Liquid Hydrogen and Deuterium. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2020; 7:1901668. [PMID: 31993284 PMCID: PMC6974937 DOI: 10.1002/advs.201901668] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Revised: 11/04/2019] [Indexed: 06/10/2023]
Abstract
The insulator-to-metal transition in dense fluid hydrogen is an essential phenomenon in the study of gas giant planetary interiors and the physical and chemical behavior of highly compressed condensed matter. Using direct fast laser spectroscopy techniques to probe hydrogen and deuterium precompressed in a diamond anvil cell and laser heated on microsecond timescales, an onset of metal-like reflectance is observed in the visible spectral range at P >150 GPa and T ≥ 3000 K. The reflectance increases rapidly with decreasing photon energy indicating free-electron metallic behavior with a plasma edge in the visible spectral range at high temperatures. The reflectance spectra also suggest much longer electronic collision time (≥1 fs) than previously inferred, implying that metallic hydrogen at the conditions studied is not in the regime of saturated conductivity (Mott-Ioffe-Regel limit). The results confirm the existence of a semiconducting intermediate fluid hydrogen state en route to metallization.
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Affiliation(s)
- Shuqing Jiang
- Key Laboratory of Materials PhysicsInstitute of Solid State PhysicsChinese Academy of SciencesHefeiAnhui230031China
- Geophysical LaboratoryCarnegie Institution of WashingtonWashingtonDC20015USA
| | - Nicholas Holtgrewe
- Geophysical LaboratoryCarnegie Institution of WashingtonWashingtonDC20015USA
- Department of MathematicsHoward University2400 Sixth Street NWWashingtonDC20059USA
- Present address:
US Food and Drug Administration645 S Newstead Ave.St. LouisMO63110USA
| | - Zachary M. Geballe
- Geophysical LaboratoryCarnegie Institution of WashingtonWashingtonDC20015USA
| | - Sergey S. Lobanov
- Geophysical LaboratoryCarnegie Institution of WashingtonWashingtonDC20015USA
- GFZ German Research Center for GeosciencesSection 3.6, Telegrafenberg14473PotsdamGermany
| | - Mohammad F. Mahmood
- Department of MathematicsHoward University2400 Sixth Street NWWashingtonDC20059USA
| | - R. Stewart McWilliams
- School of Physics and Astronomy and Centre for Science at Extreme ConditionsUniversity of EdinburghEdinburghEH9 3FDUK
| | - Alexander F. Goncharov
- Key Laboratory of Materials PhysicsInstitute of Solid State PhysicsChinese Academy of SciencesHefeiAnhui230031China
- Geophysical LaboratoryCarnegie Institution of WashingtonWashingtonDC20015USA
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23
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Tian C, Liu F, Yuan H, Chen H, Kuan A. First-order liquid-liquid phase transition in compressed hydrogen and critical point. J Chem Phys 2019; 150:204114. [PMID: 31153203 DOI: 10.1063/1.5096400] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
One of the fundamental problems relating to the properties of hydrogen is that of insulator-metal transition. Recent theoretical and experimental studies show that the metallization in liquid hydrogen could be a first-order phase transition and involve molecular to atomic transition. However, the location of the critical point is still an unresolved question. Earlier studies reported the critical point at a temperature of 1500-2000 K, but recent experimental observations on diamond-anvil cells show that the discontinuous transition still persists at temperatures well above 2000 K. We have carried out a detailed study on the liquid-liquid phase transition in dense hydrogen by uisng ab initio molecular dynamics simulations and found new evidence for the abrupt metallization between weakly dissociated and strongly dissociated fluid phases at temperatures as high as 3000 and 4000 K. Also, the predicted phase boundary is in excellent agreement with the recent experiments. Our results suggest that this first-order transition in liquid hydrogen likely ends in a critical point around 4000 K, which is significantly higher than the previous theoretical predictions.
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Affiliation(s)
- Chunling Tian
- School of Physical Science and Technology, Southwest University, Chongqing 400715, China
| | - Fusheng Liu
- Institute of High Pressure Physics, Southwest Jiaotong University, Chengdu 610031, China
| | - Hongkuan Yuan
- School of Physical Science and Technology, Southwest University, Chongqing 400715, China
| | - Hong Chen
- School of Physical Science and Technology, Southwest University, Chongqing 400715, China
| | - Anlong Kuan
- School of Physical Science and Technology, Southwest University, Chongqing 400715, China
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24
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Rillo G, Morales MA, Ceperley DM, Pierleoni C. Optical properties of high-pressure fluid hydrogen across molecular dissociation. Proc Natl Acad Sci U S A 2019; 116:9770-9774. [PMID: 31040212 PMCID: PMC6525540 DOI: 10.1073/pnas.1818897116] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Optical properties of compressed fluid hydrogen in the region where dissociation and metallization is observed are computed by ab initio methods and compared with recent experimental results. We confirm that at T > 3,000 K, both processes are continuous, while at T < 1,500 K, the first-order phase transition is accompanied by a discontinuity of the dc conductivity and the thermal conductivity, while both the reflectivity and absorption coefficient vary rapidly but continuously. Our results support the recent analysis of National Ignition Facility (NIF) experiments [Celliers PM, et al. (2018) Science 361:677-682], which assigned the inception of metallization to pressures where the reflectivity is ∼0.3. Our results also support the conclusion that the temperature plateau seen in laser-heated diamond-anvil cell (DAC) experiments at temperatures higher than 1,500 K corresponds to the onset of optical absorption, not to the phase transition.
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Affiliation(s)
- Giovanni Rillo
- Department of Physics, Sapienza University of Rome, 00185 Rome, Italy
| | - Miguel A Morales
- Physics Division, Lawrence Livermore National Laboratory, Livermore, CA 94550
| | - David M Ceperley
- Department of Physics, University of Illinois Urbana-Champaign, Urbana, IL 61801;
| | - Carlo Pierleoni
- Department of Physical and Chemical Sciences, University of L'Aquila, 67010 L'Aquila, Italy;
- Maison de la Simulation, CEA, CNRS, Univ. Paris-Sud, UVSQ, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
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25
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Desjarlais MP, Knudson MD, Redmer R. Comment on "Insulator-metal transition in dense fluid deuterium". Science 2019; 363:363/6433/eaaw0969. [PMID: 30898904 DOI: 10.1126/science.aaw0969] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Accepted: 02/27/2019] [Indexed: 11/02/2022]
Abstract
Celliers et al (Reports, 17 August 2018, p. 677), in an attempt to reconcile differences in inferred metallization pressures, provide an alternative temperature analysis of the Knudson et al experiments (Reports, 26 June 2015, p. 1455). We show that this reanalysis implies an anomalously low specific heat for the metallic fluid that is clearly inconsistent with first-principles calculations.
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Affiliation(s)
| | | | - Ronald Redmer
- Institute of Physics, University of Rostock, Rostock, Germany
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26
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Celliers PM, Millot M, Brygoo S, McWilliams RS, Fratanduono DE, Rygg JR, Goncharov AF, Loubeyre P, Eggert JH, Peterson JL, Meezan NB, Le Pape S, Collins GW, Jeanloz R, Hemley RJ. Response to Comment on "Insulator-metal transition in dense fluid deuterium". Science 2019; 363:363/6433/eaaw1970. [PMID: 30898900 DOI: 10.1126/science.aaw1970] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Accepted: 02/27/2019] [Indexed: 11/02/2022]
Abstract
In their comment, Desjarlais et al claim that a small temperature drop occurs after isentropic compression of fluid deuterium through the first-order insulator-metal transition. We show that their calculations do not correspond to the experimental thermodynamic path, and that thermodynamic integrations with parameters from first-principles calculations produce results in agreement with our original estimate of the temperature drop.
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Affiliation(s)
- Peter M Celliers
- Lawrence Livermore National Laboratory, Livermore, CA 94550, USA.
| | - Marius Millot
- Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
| | | | - R Stewart McWilliams
- School of Physics and Astronomy and Centre for Science at Extreme Conditions, University of Edinburgh, Edinburgh EH9 3FD, UK
| | | | - J Ryan Rygg
- Lawrence Livermore National Laboratory, Livermore, CA 94550, USA.,Department of Mechanical Engineering, Physics and Astronomy and Laboratory for Laser Energetics, University of Rochester, Rochester, NY 14623, USA
| | | | | | - Jon H Eggert
- Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
| | - J Luc Peterson
- Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
| | - Nathan B Meezan
- Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
| | | | - Gilbert W Collins
- Lawrence Livermore National Laboratory, Livermore, CA 94550, USA.,Department of Mechanical Engineering, Physics and Astronomy and Laboratory for Laser Energetics, University of Rochester, Rochester, NY 14623, USA
| | - Raymond Jeanloz
- Department of Earth and Planetary Science and Department of Astronomy, University of California, Berkeley, CA 94720, USA
| | - Russell J Hemley
- Institute of Materials Science and Department of Civil and Environmental Engineering, The George Washington University, Washington, DC 20052, USA
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27
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28
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Pierleoni C, Rillo G, Ceperley DM, Holzmann M. Electron localization properties in high pressure hydrogen at the liquid-liquid phase transition by Coupled Electron-Ion Monte Carlo. ACTA ACUST UNITED AC 2018. [DOI: 10.1088/1742-6596/1136/1/012005] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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29
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Celliers PM, Millot M, Brygoo S, McWilliams RS, Fratanduono DE, Rygg JR, Goncharov AF, Loubeyre P, Eggert JH, Peterson JL, Meezan NB, Le Pape S, Collins GW, Jeanloz R, Hemley RJ. Insulator-metal transition in dense fluid deuterium. Science 2018; 361:677-682. [PMID: 30115805 DOI: 10.1126/science.aat0970] [Citation(s) in RCA: 85] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Accepted: 05/31/2018] [Indexed: 11/02/2022]
Abstract
Dense fluid metallic hydrogen occupies the interiors of Jupiter, Saturn, and many extrasolar planets, where pressures reach millions of atmospheres. Planetary structure models must describe accurately the transition from the outer molecular envelopes to the interior metallic regions. We report optical measurements of dynamically compressed fluid deuterium to 600 gigapascals (GPa) that reveal an increasing refractive index, the onset of absorption of visible light near 150 GPa, and a transition to metal-like reflectivity (exceeding 30%) near 200 GPa, all at temperatures below 2000 kelvin. Our measurements and analysis address existing discrepancies between static and dynamic experiments for the insulator-metal transition in dense fluid hydrogen isotopes. They also provide new benchmarks for the theoretical calculations used to construct planetary models.
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Affiliation(s)
- Peter M Celliers
- Lawrence Livermore National Laboratory (LLNL), Livermore, CA 94550, USA.
| | - Marius Millot
- Lawrence Livermore National Laboratory (LLNL), Livermore, CA 94550, USA
| | | | - R Stewart McWilliams
- School of Physics and Astronomy and Centre for Science at Extreme Conditions, University of Edinburgh, Edinburgh EH9 3FD, UK
| | | | - J Ryan Rygg
- Lawrence Livermore National Laboratory (LLNL), Livermore, CA 94550, USA.,Department of Mechanical Engineering, Physics and Astronomy and Laboratory for Laser Energetics, University of Rochester, Rochester, NY 14623, USA
| | - Alexander F Goncharov
- Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015, USA
| | | | - Jon H Eggert
- Lawrence Livermore National Laboratory (LLNL), Livermore, CA 94550, USA
| | - J Luc Peterson
- Lawrence Livermore National Laboratory (LLNL), Livermore, CA 94550, USA
| | - Nathan B Meezan
- Lawrence Livermore National Laboratory (LLNL), Livermore, CA 94550, USA
| | - Sebastien Le Pape
- Lawrence Livermore National Laboratory (LLNL), Livermore, CA 94550, USA
| | - Gilbert W Collins
- Lawrence Livermore National Laboratory (LLNL), Livermore, CA 94550, USA.,Department of Mechanical Engineering, Physics and Astronomy and Laboratory for Laser Energetics, University of Rochester, Rochester, NY 14623, USA
| | - Raymond Jeanloz
- Department of Earth and Planetary Science and Department of Astronomy, University of California, Berkeley, CA 94720, USA
| | - Russell J Hemley
- Institute of Materials Science and Department of Civil and Environmental Engineering, The George Washington University, Washington, DC 20052, USA
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30
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Zhang S, Militzer B, Gregor MC, Caspersen K, Yang LH, Gaffney J, Ogitsu T, Swift D, Lazicki A, Erskine D, London RA, Celliers PM, Nilsen J, Sterne PA, Whitley HD. Theoretical and experimental investigation of the equation of state of boron plasmas. Phys Rev E 2018; 98:023205. [PMID: 30253522 DOI: 10.1103/physreve.98.023205] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2018] [Indexed: 06/08/2023]
Abstract
We report a theoretical equation of state (EOS) table for boron across a wide range of temperatures (5.1×10^{4}-5.2×10^{8} K) and densities (0.25-49 g/cm^{3}) and experimental shock Hugoniot data at unprecedented high pressures (5608±118 GPa). The calculations are performed with first-principles methods combining path-integral Monte Carlo (PIMC) at high temperatures and density-functional-theory molecular-dynamics (DFT-MD) methods at lower temperatures. PIMC and DFT-MD cross-validate each other by providing coherent EOS (difference <1.5 Hartree/boron in energy and <5% in pressure) at 5.1×10^{5} K. The Hugoniot measurement is conducted at the National Ignition Facility using a planar shock platform. The pressure-density relation found in our shock experiment is on top of the shock Hugoniot profile predicted with our first-principles EOS and a semiempirical EOS table (LEOS 50). We investigate the self-diffusivity and the effect of thermal and pressure-driven ionization on the EOS and shock compression behavior in high-pressure and -temperature conditions. We also study the sensitivity of a polar direct-drive exploding pusher platform to pressure variations based on applying pressure multipliers to LEOS 50 and by utilizing a new EOS model based on our ab initio simulations via one-dimensional radiation-hydrodynamic calculations. The results are valuable for future theoretical and experimental studies and engineering design in high-energy density research.
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Affiliation(s)
- Shuai Zhang
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - Burkhard Militzer
- Department of Earth and Planetary Science, University of California, Berkeley, California 94720, USA
- Department of Astronomy, University of California, Berkeley, California 94720, USA
| | - Michelle C Gregor
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - Kyle Caspersen
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - Lin H Yang
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - Jim Gaffney
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - Tadashi Ogitsu
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - Damian Swift
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - Amy Lazicki
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - D Erskine
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - Richard A London
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - P M Celliers
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - Joseph Nilsen
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - Philip A Sterne
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - Heather D Whitley
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
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Metallization and molecular dissociation of dense fluid nitrogen. Nat Commun 2018; 9:2624. [PMID: 29980680 PMCID: PMC6035179 DOI: 10.1038/s41467-018-05011-z] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2018] [Accepted: 06/06/2018] [Indexed: 11/26/2022] Open
Abstract
Diatomic nitrogen is an archetypal molecular system known for its exceptional stability and complex behavior at high pressures and temperatures, including rich solid polymorphism, formation of energetic states, and an insulator-to-metal transformation coupled to a change in chemical bonding. However, the thermobaric conditions of the fluid molecular–polymer phase boundary and associated metallization have not been experimentally established. Here, by applying dynamic laser heating of compressed nitrogen and using fast optical spectroscopy to study electronic properties, we observe a transformation from insulating (molecular) to conducting dense fluid nitrogen at temperatures that decrease with pressure and establish that metallization, and presumably fluid polymerization, occurs above 125 GPa at 2500 K. Our observations create a better understanding of the interplay between molecular dissociation, melting, and metallization revealing features that are common in simple molecular systems. Nitrogen is a model system still presenting unknown behaviors at the pressures and temperatures typical of deep planets’ interiors. Here the authors explore, by pulsed laser heating in a diamond anvil cell and optical measurements, the metallization and non-molecular states of nitrogen in a previously unexplored domain above 1 Mbar and at 2000-7000K.
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32
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Calcavecchia F, Kühne TD. Metal-Insulator Transition of Solid Hydrogen by the Antisymmetric Shadow Wave Function. ACTA ACUST UNITED AC 2018. [DOI: 10.1515/zna-2018-0180] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Abstract
We revisit the pressure-induced molecular-atomic metal-insulator transition of solid hydrogen by means of variational quantum Monte Carlo simulations based on the antisymmetric shadow wave function. For the purpose of facilitating the study of the electronic structure of large-scale fermionic systems, the shadow wave function formalism is extended by a series of technical advancements as implemented in our HswfQMC code. Among others, these improvements include a revised optimization method for the employed shadow wave function and an enhanced treatment of periodic systems with long-range interactions. It is found that the superior accuracy of the antisymmetric shadow wave function results in a significantly increased transition pressure with respect to previous theoretical estimates.
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Affiliation(s)
- Francesco Calcavecchia
- LPMMC, UMR 5493 of CNRS , Université Grenoble Alpes , 38042 Grenoble , France
- Institute of Physics , Johannes Gutenberg University , Staudingerweg 7 , D-55128 Mainz , Germany
- Graduate School of Excellence Materials Science in Mainz , Staudingerweg 9 , D-55128 Mainz , Germany
| | - Thomas D. Kühne
- Dynamics of Condensed Matter, Department of Chemistry , University of Paderborn , Warburger Str. 100 , D-33098 Paderborn , Germany
- Paderborn Center for Parallel Computing , University of Paderborn , Warburger Str. 100 , D-33098 Paderborn , Germany
- Center for Sustainable Systems Design , University of Paderborn , Warburger Str. 100 , D-33098 Paderborn , Germany
- Institute for Lightweight Design , University of Paderborn , Warburger Str. 100 , D-33098 Paderborn , Germany
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33
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Zhao G, Wang H, Hu DM, Ding MC, Zhao XG, Yan JL. Anomalous phase behavior of first-order fluid-liquid phase transition in phosphorus. J Chem Phys 2018; 147:204501. [PMID: 29195280 DOI: 10.1063/1.4999009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Although the existence of liquid-liquid phase transition has become more and more convincing, whether it will terminate at a critical point and what is the order parameter are still open. To explore these questions, we revisit the fluid-liquid phase transition (FLPT) in phosphorus (P) and study its phase behavior by performing extensive first-principles molecular dynamics simulations. The FLPT observed in experiments is well reproduced, and a fluid-liquid critical point (FLCP) at T = 3000 ∼ 3500 K, P = 1.5-2.0 Kbar is found. With decreasing temperature from the FLCP along the transition line, the density difference (Δρ) between two coexisting phases first increases from zero and then anomalously decreases; however, the entropy difference (ΔS) continuously increases from zero. These features suggest that an order parameter containing contributions from both the density and the entropy is needed to describe the FLPT in P, and at least at low temperatures, the entropy, instead of the density, governs the FLPT.
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Affiliation(s)
- G Zhao
- School of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025, People's Republic of China
| | - H Wang
- School of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025, People's Republic of China
| | - D M Hu
- School of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025, People's Republic of China
| | - M C Ding
- School of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025, People's Republic of China
| | - X G Zhao
- School of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025, People's Republic of China
| | - J L Yan
- School of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025, People's Republic of China
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34
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Zaghoo M. Dynamic conductivity and partial ionization in dense fluid hydrogen. Phys Rev E 2018; 97:043205. [PMID: 29758665 DOI: 10.1103/physreve.97.043205] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Indexed: 11/07/2022]
Abstract
A theoretical description for optical conduction experiments in dense fluid hydrogen is presented. Different quantum statistical approaches are used to describe the mechanism of electronic transport in hydrogen's high-temperature dense phase. We show that at the onset of the metallic transition, optical conduction could be described by a strong rise in atomic polarizability, due to increased ionization, whereas in the highly degenerate limit, the Ziman weak scattering model better accounts for the observed saturation of reflectance. The inclusion of effects of partial ionization in the highly degenerate region provides great agreement with experimental results. Hydrogen's fluid metallic state is revealed to be a partially ionized free-electron plasma. Our results provide some of the first theoretical transport models that are experimentally benchmarked, as well as an important guide for future studies.
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Affiliation(s)
- Mohamed Zaghoo
- Laboratory for Laser Energetics, University of Rochester, New York 14620, USA and Lyman Laboratory of Physics, Harvard University, Cambridge, Massachusetts 02143, USA
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35
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Zhang S, Militzer B, Benedict LX, Soubiran F, Sterne PA, Driver KP. Path integral Monte Carlo simulations of dense carbon-hydrogen plasmas. J Chem Phys 2018; 148:102318. [DOI: 10.1063/1.5001208] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Shuai Zhang
- Department of Earth and Planetary Science, University of California, Berkeley, California 94720, USA
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - Burkhard Militzer
- Department of Earth and Planetary Science, University of California, Berkeley, California 94720, USA
- Department of Astronomy, University of California, Berkeley, California 94720, USA
| | - Lorin X. Benedict
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - François Soubiran
- Department of Earth and Planetary Science, University of California, Berkeley, California 94720, USA
| | - Philip A. Sterne
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - Kevin P. Driver
- Department of Earth and Planetary Science, University of California, Berkeley, California 94720, USA
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
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36
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Rillo G, Morales MA, Ceperley DM, Pierleoni C. Coupled electron-ion Monte Carlo simulation of hydrogen molecular crystals. J Chem Phys 2018; 148:102314. [DOI: 10.1063/1.5001387] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- Giovanni Rillo
- Department of Physics, Sapienza University of Rome, Rome, Italy
| | - Miguel A. Morales
- Physics Division, Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - David M. Ceperley
- Department of Physics, University of Illinois Urbana-Champaign, Champaign, llinois 61801, USA
| | - Carlo Pierleoni
- Department of Physical and Chemical Sciences, University of L’Aquila, L’Aquila, Italy
- Maison de la Simulation, CEA, CNRS, Univ. Paris-Sud, UVSQ, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
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37
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Kang D, Dai J. Dynamic electron-ion collisions and nuclear quantum effects in quantum simulation of warm dense matter. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:073002. [PMID: 29186001 DOI: 10.1088/1361-648x/aa9e29] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The structural, thermodynamic and transport properties of warm dense matter (WDM) are crucial to the fields of astrophysics and planet science, as well as inertial confinement fusion. WDM refers to the states of matter in a regime of temperature and density between cold condensed matter and hot ideal plasmas, where the density is from near-solid up to ten times solid density, and the temperature between 0.1 and 100 eV. In the WDM regime, matter exhibits moderately or strongly coupled, partially degenerate properties. Therefore, the methods used to deal with condensed matter and isolated atoms need to be properly validated for WDM. It is therefore a big challenge to understand WDM within a unified theoretical description with reliable accuracy. Here, we review the progress in the theoretical study of WDM with state-of-the-art simulations, i.e. quantum Langevin molecular dynamics and first principles path integral molecular dynamics. The related applications for WDM are also included.
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Affiliation(s)
- Dongdong Kang
- Department of Physics, National University of Defense Technology, Changsha, Hunan 410073, People's Republic of China
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38
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Mazzola G, Helled R, Sorella S. Phase Diagram of Hydrogen and a Hydrogen-Helium Mixture at Planetary Conditions by Quantum Monte Carlo Simulations. PHYSICAL REVIEW LETTERS 2018; 120:025701. [PMID: 29376719 DOI: 10.1103/physrevlett.120.025701] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Indexed: 06/07/2023]
Abstract
Understanding planetary interiors is directly linked to our ability of simulating exotic quantum mechanical systems such as hydrogen (H) and hydrogen-helium (H-He) mixtures at high pressures and temperatures. Equation of state (EOS) tables based on density functional theory are commonly used by planetary scientists, although this method allows only for a qualitative description of the phase diagram. Here we report quantum Monte Carlo (QMC) molecular dynamics simulations of pure H and H-He mixture. We calculate the first QMC EOS at 6000 K for a H-He mixture of a protosolar composition, and show the crucial influence of He on the H metallization pressure. Our results can be used to calibrate other EOS calculations and are very timely given the accurate determination of Jupiter's gravitational field from the NASA Juno mission and the effort to determine its structure.
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Affiliation(s)
| | - Ravit Helled
- Institute for Computational Science, Center for Theoretical Astrophysics and Cosmology, University of Zurich, 8057 Zurich, Switzerland
| | - Sandro Sorella
- International School for Advanced Studies (SISSA) and INFM Democritos National Simulation Center, via Bonomea 265, 34136 Trieste, Italy
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39
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Groth S, Dornheim T, Sjostrom T, Malone FD, Foulkes WMC, Bonitz M. Ab initio Exchange-Correlation Free Energy of the Uniform Electron Gas at Warm Dense Matter Conditions. PHYSICAL REVIEW LETTERS 2017; 119:135001. [PMID: 29341671 DOI: 10.1103/physrevlett.119.135001] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Indexed: 06/07/2023]
Abstract
In a recent Letter [T. Dornheim et al., Phys. Rev. Lett. 117, 156403 (2016)PRLTAO0031-900710.1103/PhysRevLett.117.156403], we presented the first quantum Monte Carlo (QMC) results for the warm dense electron gas in the thermodynamic limit. However, a complete parametrization of the exchange-correlation free energy with respect to density, temperature, and spin polarization remained out of reach due to the absence of (i) accurate QMC results below θ=k_{B}T/E_{F}=0.5 and (ii) QMC results for spin polarizations different from the paramagnetic case. Here we overcome both remaining limitations. By closing the gap to the ground state and by performing extensive QMC simulations for different spin polarizations, we are able to obtain the first completely ab initio exchange-correlation free energy functional; the accuracy achieved is an unprecedented ∼0.3%. This also allows us to quantify the accuracy and systematic errors of various previous approximate functionals.
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Affiliation(s)
- Simon Groth
- Institut für Theoretische Physik und Astrophysik, Christian-Albrechts-Universität zu Kiel, D-24098 Kiel, Germany
| | - Tobias Dornheim
- Institut für Theoretische Physik und Astrophysik, Christian-Albrechts-Universität zu Kiel, D-24098 Kiel, Germany
| | - Travis Sjostrom
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Fionn D Malone
- Department of Physics, Imperial College London, Exhibition Road, London SW7 2AZ, United Kingdom
- Physics Division, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
| | - W M C Foulkes
- Department of Physics, Imperial College London, Exhibition Road, London SW7 2AZ, United Kingdom
| | - Michael Bonitz
- Institut für Theoretische Physik und Astrophysik, Christian-Albrechts-Universität zu Kiel, D-24098 Kiel, Germany
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40
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Zha CS, Liu H, Tse JS, Hemley RJ. Melting and High P-T Transitions of Hydrogen up to 300 GPa. PHYSICAL REVIEW LETTERS 2017; 119:075302. [PMID: 28949699 DOI: 10.1103/physrevlett.119.075302] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Indexed: 06/07/2023]
Abstract
High P-T Raman spectra of hydrogen in the vibron and lattice mode regions were measured up to 300 GPa and 900 K using externally heated diamond anvil cell techniques. A new melting line determined from the disappearance of lattice mode excitations was measured directly for the first time above 140 GPa. The results differ from theoretical predictions and extrapolations from lower pressure melting relations. In addition, discontinuities in Raman frequencies are observed as a function of pressure and temperature indicative of phase transition at these conditions. The appearance of a new Raman feature near 2700 cm^{-1} at ∼300 GPa and 370 K indicates the transformation to a new crystalline phase. Theoretical calculations of the spectrum suggest the new phase is the proposed Cmca-4 metallic phase. The transition pressure is close to that of a recently reported transition observed on dynamic compression.
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Affiliation(s)
- Chang-Sheng Zha
- Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015, USA
| | - Hanyu Liu
- Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015, USA
| | - John S Tse
- Department of Physics, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B2, Canada
| | - Russell J Hemley
- Department of Civil and Environmental Engineering, The George Washington University, Washington, DC 20052, USA
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41
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Dias RP, Silvera IF. Observation of the Wigner-Huntington transition to metallic hydrogen. Science 2017; 355:715-718. [DOI: 10.1126/science.aal1579] [Citation(s) in RCA: 357] [Impact Index Per Article: 51.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Accepted: 01/13/2017] [Indexed: 11/02/2022]
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42
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Mazzola G, Sorella S. Accelerating ab initio Molecular Dynamics and Probing the Weak Dispersive Forces in Dense Liquid Hydrogen. PHYSICAL REVIEW LETTERS 2017; 118:015703. [PMID: 28106448 DOI: 10.1103/physrevlett.118.015703] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Indexed: 06/06/2023]
Abstract
We propose an ab initio molecular dynamics method, capable of dramatically reducing the autocorrelation time required for the simulation of classical and quantum particles at finite temperatures. The method is based on an efficient implementation of a first order Langevin dynamics modified by means of a suitable, position dependent acceleration matrix S. Here, we apply this technique to both Lennard-Jones models, to demonstrate the accuracy and speeding-up of the sampling, and within a quantum Monte Carlo based wave function approach, for determining the phase diagram of high-pressure hydrogen with simulations much longer than the autocorrelation time. With the proposed method, we are able to equilibrate in a few hundred steps even close to the liquid-liquid phase transition (LLT). Within our approach, we find that the LLT transition is consistent with recent density functionals predicting a much larger transition pressure when the long range dispersive forces are taken into account.
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Affiliation(s)
| | - Sandro Sorella
- International School for Advanced Studies (SISSA) Via Beirut 2, 4 34014 Trieste, Italy and INFM Democritos National Simulation Center, Via Beirut 2-4, I-34014 Trieste, Italy
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