Thomas-Fermi<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>Z</mml:mi></mml:math>-scaling laws and coupling stabilization for plasmas

Arnault, Philippe; Clérouin, Jean; Robert, G.; Ticknor, Christopher; Kress, Joel D.; Collins, L. A.

doi:10.1103/physreve.88.063106

Cited by 20 publications

(18 citation statements)

References 39 publications

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“…This is particularly acute for KS calculations, where a poor scaling of the computational cost with temperature limits it to low temperatures. The OF method does not suffer from this poor scaling but is still very expensive, typically limiting the number of particles in the MD simulation to a few 100's [8][9][10][11]. DFT-MD calculations are especially challenging for mixtures, where asymmetries in masses and number fractions increase the computational 1 The notation means a carbon-hydrogen mixture in the ratio 0.424:0.576.…”

Section: Introductionmentioning

confidence: 99%

Integral equation model for warm and hot dense mixtures

et al. 2014

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In Starrett and Saumon [Phys. Rev. E 87, 013104 (2013)] a model for the calculation of electronic and ionic structures of warm and hot dense matter was described and validated. In that model the electronic structure of one 'atom' in a plasma is determined using a density functional theory based average-atom (AA) model, and the ionic structure is determined by coupling the AA model to integral equations governing the fluid structure. That model was for plasmas with one nuclear species only. Here we extend it to treat plasmas with many nuclear species, i.e. mixtures, and apply it to a carbon-hydrogen mixture relevant to inertial confinement fusion experiments. Comparison of the predicted electronic and ionic structures with orbital-free and Kohn-Sham molecular dynamics simulations reveals excellent agreement wherever chemical bonding is not significant.

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Section: Introductionmentioning

confidence: 99%

Integral equation model for warm and hot dense mixtures

et al. 2014

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“…This prescription defines an effective OCP coupling parameter [20], Γ ef f , and hence an effective ionization state Q. This procedure has been successfully used in a recent study of isochorically heated dense tungsten, exhibiting the so-called Γ-plateau feature [21,22].…”

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confidence: 99%

Evidence for out-of-equilibrium states in warm dense matter probed by x-ray Thomson scattering

et al. 2015

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A recent and unexpected discrepancy between ab initio simulations and the interpretation of a laser shock experiment on aluminum, probed by X-ray Thomson scattering (XRTS), is addressed.The ion-ion structure factor deduced from the XRTS elastic peak (ion feature) is only compatible with a strongly coupled out-of-equilibrium state. Orbital free molecular dynamics simulations with ions colder than the electrons are employed to interpret the experiment. The relevance of decoupled temperatures for ions and electrons is discussed. The possibility that it mimics a transient, or metastable, out-of-equilibrium state after melting is also suggested.

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“…Orbital-free (OF) DFT-MD 1 [8] does not suffer from the poor temperature scaling of KS-DFT-MD, and it has been applied to a wide range of plasma conditions (eg. [9,10]). This benefit comes at the cost of physical accuracy, though there has been significant recent progress in improving OFMD towards a KS-DFT-MD level of accuracy (eg.…”

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confidence: 99%

Pseudoatom molecular dynamics

2015

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A new approach to simulating warm and hot dense matter that combines density functional theory based calculations of the electronic structure to classical molecular dynamics simulations with pair interaction potentials is presented. The new method, which we call pseudoatom molecular dynamics (PAMD), can be applied to single or multi-component plasmas. It gives equation of state and selfdiffusion coefficients with an accuracy comparable to ab-initio simulations but is computationally much more efficient.PACS numbers: 51.20.+d, 51.30.+i, 52.25.Kn, 52.65.Yy The challenge of accurately modeling dense plasmas over a wide range of conditions represents an unsolved problem lying at the heart of many important phenomena such as inertial confinement fusion [1], exoplanets and white dwarfs [2,3]. The production of large scale and accurate tabulations of data such as equation of state and transport coefficients as a function of density and temperature is a formidable task, requiring a consistent quantum mechanical treatment of the many-electron problem together with a classical treatment of the nuclear motion. The atoms in the plasma may have bound states or be fully ionized, the electrons may be fully degenerate or approaching their classical limit. The nuclear fluid can range from weakly through to strongly coupled. A consistent, reliable and accurate treatment across all these physical regimes with an approach that remains computationally tractable remains as an open problem.Plasmas of interest are typically one to thousands of times solid density, and have temperatures from about 1eV (∼10kK) to thousands of eV. The difficulty of creating and controlling such plasmas in the laboratory explains the lack of experimental data to guide theoretical development, though ongoing campaigns at National Ignition Facility [4] and elsewhere (eg.[5]), and recent advances in X-ray scattering techniques [6] are beginning to shed light on this problem.From a simulations perspective, powerful and complex tools exist that can provide benchmark calculations. In the lower temperature regime (a few eV) one such tool is Kohn-Sham (KS) density functional theory molecular dynamics (DFT-MD) (eg. [7]). Electrons are treated quantum mechanically through KS-DFT and ions are propagated with classical MD. The simulations are very computationally expensive and this cost scales poorly with temperature, limiting the method to lower temperatures. In practice KS-DFT-MD also relies on a pseudopotential approximation, which reduces the computational overhead by limiting the number of actively modeled electrons, through an ad hoc modification of the electron- (r), n ext e (r) and n P A e (r), as described in the text. Also shown is the bound state (or ion) contribution (n ion e (r)) to n P A e (r) and the valence electron contribution n scr e (r). The double peak structure in n ion e (r) reflects the bound state shell structure in the aluminum ion, while the oscillations in the valence contribution n scr e (r) are the well known Friedel oscillations, whic...

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Thomas-FermiZ-scaling laws and coupling stabilization for plasmas

Cited by 20 publications

References 39 publications

Integral equation model for warm and hot dense mixtures

Integral equation model for warm and hot dense mixtures

Evidence for out-of-equilibrium states in warm dense matter probed by x-ray Thomson scattering

Pseudoatom molecular dynamics

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