First-principles simulations of warm dense lithium fluoride

Driver, Kevin P.; Militzer, Burkhard

doi:10.1103/physreve.95.043205

Cited by 36 publications

(27 citation statements)

References 81 publications

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“…Rigorous discussions of the PIMC [76][77][78] and DFT molecular dynamics (DFT-MD) [79][80][81] methods have been provided in previous works, and the details of our simulations have been presented in some of our previous publications [74,75,[82][83][84][85][86][87][88][89][90][91][92][93]. Here, we summarize the methods and provide the simulation parameters specific to simulations of aluminum plasma.…”

Section: Simulation Methodsmentioning

confidence: 99%

Path integral Monte Carlo simulations of warm dense aluminum

2018

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We perform first-principles path integral Monte Carlo (PIMC) and density functional theory molecular dynamics (DFT-MD) calculations to explore warm dense matter states of aluminum. Our equation of state (EOS) simulations cover a wide density-temperature range of 0.1-32.4gcm^{-3} and 10^{4}-10^{8} K. Since PIMC and DFT-MD accurately treat effects of the atomic shell structure, we find two compression maxima along the principal Hugoniot curve attributed to K-shell and L-shell ionization. The results provide a benchmark for widely used EOS tables, such as SESAME, QEOS, and models based on Thomas-Fermi and average-atom techniques. A subsequent multishock analysis provides a quantitative assessment for how much heating occurs relative to an isentrope in multishock experiments. Finally, we compute heat capacity, pair-correlation functions, the electronic density of states, and 〈Z〉 to reveal the evolution of the plasma structure and ionization behavior.

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Section: Simulation Methodsmentioning

confidence: 99%

Path integral Monte Carlo simulations of warm dense aluminum

2018

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“…The 1.08 factor equals the ratio of the density of defect-free diamond, 3.515 g cm −3 , and the initial density of the porous diamond in the experiment 3.25 g cm −3 . This scaling has been shown to work fairly well in shock compression experiments on porous materials [51][52][53][54][55][56]. If the shock Hugoniot curve for an initial density ρ A 0 is known but the curve for the initial density ρ B 0 is needed, one can approximately scale the densities of the original Hugoniot curve by the ratio of ρ B 0 /ρ A 0 .…”

Section: Ramp Compression Experiments Of Diamond and Equation Of Statementioning

confidence: 78%

Model of Ramp Compression of Diamond from Ab Initio Simulations

González-Cataldo,

Godwal,

Driver

et al. 2021

Preprint

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Ramp compression experiments characterize high-pressure states of matter at temperatures well below those present in shock compression. However, because temperature is typically not directly measured during ramp compression, it is uncertain how much heating occurs under these shock-free conditions. Here, we performed a series of ab initio simulations on carbon in order to match the density-stress measurements of Smith et al. [Smith, et al., Nature 511, 330 (2014)]. We considered isotropically as well as uniaxially compressed solid carbon in the diamond and BC8 phases, with and without defects, as well as liquid carbon. Our idealized model ascribes heating during ramp compression to an initially uniaxially compressed cell transforming isochorically into an isotropically (hydrostatic equivalent) compressed state having lower internal energy, hence higher temperature so as to conserve energy. Multiple such heating events can occur during a single ramp experiment, leading to higher temperatures than with isentropic compression. Comparison with experiments shows that heating alone does not explain the equation of state measurements on diamond, instead implying that a significant uniaxial stress component remains present at high compression. The temperature predictions of our ramp compression model remain to be verified with future laboratory measurements.

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“…For PIMC simulations, we use the CUPID code [26][27][28] with Hartree-Fock nodes [29][30][31]. For DFT-MD simulations, we employ Kohn-Sham DFT simulation techniques as implemented in the Vienna Ab initio Simulation Package (VASP) [32] using the projector augmented-wave (PAW) method [33,34], and molecular dynamics is performed in the NVT ensemble, regulated with a Nosé thermostat.…”

Section: Methodsmentioning

confidence: 99%

Thermal and Pressure Ionization in Warm, Dense MgSiO$_3$ Studied with First-Principles Computer Simulations

González-Cataldo,

Militzer

2020

Preprint

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Using path integral Monte Carlo and density functional molecular dynamics (DFT-MD) simulations, we study the properties of MgSiO 3 enstatite in the regime of warm dense matter. We generate a consistent equation of state (EOS) that spans across a wide range of temperatures and densities (10 4 -10 7 K and 6.42-64.16 g cm −3 ). We derive the shock Hugoniot curve, that is in good agreement with the experiments. We identify the boundary between the regimes of thermal ionization and pressure ionization by locating where the internal energy at constant temperature attains a minimum as a function of density or pressure. At low density, the internal energy decreases with increasing density as the weight of free states changes. Thermal ionization dominates. Conversely, at high density, in the regime of pressure ionization, the internal energy increases with density. We determine the boundary between the two regimes and show that the compression maximum along the shock Hugoniot curve occurs because K shell electrons become thermally ionized rather than pressure ionized.

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First-principles simulations of warm dense lithium fluoride

Cited by 36 publications

References 81 publications

Path integral Monte Carlo simulations of warm dense aluminum

Path integral Monte Carlo simulations of warm dense aluminum

Model of Ramp Compression of Diamond from Ab Initio Simulations

Thermal and Pressure Ionization in Warm, Dense MgSiO$_3$ Studied with First-Principles Computer Simulations

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