Laser-driven single shock compression of fluid deuterium from 45 to 220 GPa

Hicks, D. G.; Boehly, T. R.; Celliers, P. M.; Eggert, J. H.; Moon, Stephen J.; Meyerhofer, D. D.; Collins, G. W.

doi:10.1103/physrevb.79.014112

Cited by 141 publications

(29 citation statements)

References 61 publications

(105 reference statements)

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“…Very recently ͑2009͒, measurements at higher pressures-220 GPa-have been made using laser ablation as a shock source, 55 which indicate a compressibility of ϳ4.2 below 110 GPa, rising to a maximum compression of 5 at 160 GPa, in excellent agreement with our prior prediction. Indeed, the eFF single shock Hugoniot curves smoothly in such a way that it passes through the error margins of nearly all of the available experimental data.…”

Section: ͑26͒supporting

confidence: 81%

“…The heightened stability of a molecularlike phase may result from the transient formation of a metallic phase, where electrons hop freely between hydrogen atoms and molecules; we can observe with eFF this electron hopping behavior. Overall, the phenomenon of electron hopping provides an explanation for the enhanced reflectivity of dense hydrogen observed above 25 GPa in several experiments, 55,68 and may contribute to the enhanced compressibility of dense hydrogen ͑relative to an ideal gas of atoms͒ along the primary shock Hugoniot.…”

Section: ͑26͒mentioning

confidence: 83%

“…16 and also add new comparisons to recent experimental data. 55 The behavior of hydrogen at extreme pressures ͑hundreds of gigapascals͒ and moderate temperatures ͑thou-sands of degrees͒ has relevance to the phase partitioning of giant planetary interiors, 56 as well as the design of systems for inertial confinement fusion. 57 Warm dense hydrogen has been discovered to have metallic properties ͑3000 K, 140 GPa͒, 58 and it has been proposed that its enhanced conductivity may involve the participation of electronically excited mixtures of H 2 molecules, H atoms, and other species along with free protons and electrons.…”

Section: A Thermodynamics Of Warm Dense Hydrogenmentioning

confidence: 99%

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The dynamics of highly excited electronic systems: Applications of the electron force field

Goddard

2009

The Journal of Chemical Physics

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Highly excited heterogeneous complex materials are essential elements of important processes, ranging from inertial confinement fusion to semiconductor device fabrication. Understanding the dynamics of these systems has been challenging because of the difficulty in extracting mechanistic information from either experiment or theory. We describe here the electron force field ͑eFF͒ approximation to quantum mechanics which provides a practical approach to simulating the dynamics of such systems. eFF includes all the normal electrostatic interactions between electrons and nuclei and the normal quantum mechanical description of kinetic energy for the electrons, but contains two severe approximations: first, the individual electrons are represented as floating Gaussian wave packets whose position and size respond instantaneously to various forces during the dynamics; and second, these wave packets are combined into a many-body wave function as a Hartree product without explicit antisymmetrization. The Pauli principle is accounted for by adding an extra spin-dependent term to the Hamiltonian. These approximations are a logical extension of existing approaches to simulate the dynamics of fermions, which we review. In this paper, we discuss the details of the equations of motion and potentials that form eFF, and evaluate the ability of eFF to describe ground-state systems containing covalent, ionic, multicenter, and/or metallic bonds. We also summarize two eFF calculations previously reported on electronically excited systems: ͑1͒ the thermodynamics of hydrogen compressed up to ten times liquid density and heated up to 200 000 K; and ͑2͒ the dynamics of Auger fragmentation in a diamond nanoparticle, where hundreds of electron volts of excitation energy are dissipated over tens of femtoseconds. These cases represent the first steps toward using eFF to model highly excited electronic processes in complex materials.

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Section: ͑26͒supporting

confidence: 81%

Section: ͑26͒mentioning

confidence: 83%

Section: A Thermodynamics Of Warm Dense Hydrogenmentioning

confidence: 99%

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The dynamics of highly excited electronic systems: Applications of the electron force field

Goddard

2009

The Journal of Chemical Physics

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“…Dynamic compression experiments first indicated changes in electrical conductivity (5) and density from shadow radiography (6). Discrepancies in the equation of state (e.g., at higher pressures and temperatures) have largely been resolved, but differences remain (35,36). But in comparison with static compression studies the range of diagnostic tools has been limited from the standpoint of probes of the state of bonding, which is needed to constrain different theoretical models that predict dissociation and the degree of ionization.…”

mentioning

confidence: 99%

Bonding changes in hot fluid hydrogen at megabar pressures

Subramanian

Goncharov

Struzhkin

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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Raman spectroscopy in laser-heated diamond anvil cells has been employed to probe the bonding state and phase diagram of dense hydrogen up to 140 GPa and 1,500 K. The measurements were made possible as a result of the development of new techniques for containing and probing the hot, dense fluid, which is of fundamental importance in physics, planetary science, and astrophysics. A pronounced discontinuous softening of the molecular vibron was found at elevated temperatures along with a large broadening and decrease in intensity of the roton bands. These phenomena indicate the existence of a state of the fluid having significantly modified intramolecular bonding. The results are consistent with the existence of a pressure-induced transformation in the fluid related to the presence of a temperature maximum in the melting line as a function of pressure.diamond anvil cell | high pressure | Raman scattering | laser heating | melting T he response of the covalent bond of molecular hydrogen to chemical, density, and thermal perturbations is central to a broad range of problems in the physical sciences. In particular, information on the behavior of hydrogen at very high pressures and variable temperatures is needed to explore the theoretically predicted molecular-atomic transition in the solid (1), the existence of an expanded stability field of the fluid and novel lowtemperature diffusive states (2-4), and the nature of reported transitions in the fluid at megabar pressures (5, 6). Hydrogen is also important for understanding the behavior of materials in general at extreme conditions (7,8). Hydrogen is the most abundant element in the cosmos, and the nature of hydrogen at high temperatures and pressures is crucial for understanding the interiors of large gaseous planets, including exoplanets, and other astrophysical bodies (9, 10). The latter includes detailing the sequence of transitions associated with the onset of nuclear processes in ultrahigh density hydrogen plasmas inside very large astrophysical bodies.There are numerous questions surrounding the behavior of dense hydrogen in the condensed matter domain of megabar (10 11 Pa) pressures and of order 10 3 K temperatures. Experiments and first-principles calculations indicate a temperature maximum in the melting curve as a function pressure near 100 GPa and 1,000 K (11-14). Near 140 GPa and higher temperatures, there is evidence for onset of electrical conductivity (5) and an increase in density (6). The downturn in the melting line has been predicted in various calculations, but the degree of ionization and dissociation in the molecular fluid and an onset of electrical conductivity at higher temperature vary among calculations (15)(16)(17)(18)(19)(20). Characterizing the bonding state of the dense, hot fluid under these conditions is required to search for molecular dissociation and to test competing mechanisms for the onset of electrical conductivity (6,15,17,20,21). The theoretical and experimental indications of a presence of the maximum in the melting line (11,...

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“…Particularly relevant for our current understanding of the phase diagram and the Equation of State (EOS) of compressed hydrogen has been the determination of the primary and secondary Hugoniots lines of deuterium which could be directly compared with experimental data [40,61]. RPIMC predictions for the principal Hugoniot of deuterium were first in disagreement with pulsed laser-produced shock compression experiments [62][63][64], but were later confirmed by magnetically generated shock compression experiments at the Z-pinch machine [65][66][67][68][69][70] and by converging explosive-driven shock waves techniques [71,72]. Also relevant for the development and fine tuning of simulation methods for Warm Dense Matter has been the comparison with the less demanding, but also less fundamental methods based on Density Functional Theory (either Kohn-Sham or Orbital-Free flavours).…”

Section: High-pressure Hydrogenmentioning

confidence: 92%

First Principles Methods: A Perspective from Quantum Monte Carlo

Morales

Clay

Pierleoni

et al. 2013

Entropy

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Quantum Monte Carlo methods are among the most accurate algorithms for predicting properties of general quantum systems. We briefly introduce ground state, path integral at finite temperature and coupled electron-ion Monte Carlo methods, their merits and limitations. We then discuss recent calculations using these methods for dense liquid hydrogen as it undergoes a molecular/atomic (metal/insulator) transition. We then discuss a procedure that can be used to assess electronic density functionals, which in turn can be used on a larger scale for first principles calculations and apply this technique to dense hydrogen and liquid water.

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Laser-driven single shock compression of fluid deuterium from 45 to 220 GPa

Cited by 141 publications

References 61 publications

The dynamics of highly excited electronic systems: Applications of the electron force field

The dynamics of highly excited electronic systems: Applications of the electron force field

Bonding changes in hot fluid hydrogen at megabar pressures

First Principles Methods: A Perspective from Quantum Monte Carlo

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