First-principles prediction of the softening of the silicon shock Hugoniot curve

Hu, S. X.; Militzer, Burkhard; Collins, L. A.; Driver, Kevin P.; Kress, Joel D.

doi:10.1103/physrevb.94.094109

Cited by 45 publications

(50 citation statements)

References 69 publications

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“…Based on this comparison and the K shell ionization analysis of MgO in Fig. 4 we conclude that the upper part of the high com- [30,71], oxygen [73], neon [31], aluminum [38], and silicon [32,36]. This comparison supports the interpretation that the broad temperature interval where the compression of MgO exceeds 4.5 can be attributed to the ionization of the K shell electrons of the oxygen and magnesium nuclei.…”

Section: Single and Multi Shock Hugoniot Curvessupporting

confidence: 77%

Magnesium oxide at extreme temperatures and pressures studied with first-principles simulations

Soubiran

González‐Cataldo

Driver

et al. 2019

The Journal of Chemical Physics

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We combine two first-principles computer simulation techniques, path integral Monte-Carlo and density functional theory molecular dynamics, to determine the equation of state of magnesium oxide in the regime of warm dense matter, with densities ranging from 0.35 to 71 g cm −3 and temperatures from 10,000 K to 5 × 10 8 K. These conditions are relevant for the interiors of giant planets and stars as well as for shock wave compression measurements and inertial confinement fusion experiments. We study the electronic structure of MgO and the ionization mechanisms as a function of density and temperature. We show that the L-shell orbitals of magnesium and oxygen hybridize at high density. This results into a gradual ionization of the L-shell with increasing density and temperature. In this regard, MgO behaves differently from pure oxygen, which is reflected in the shape of the MgO principal shock Hugoniot curve. The curve of oxygen shows two compression maxima, while that of MgO shows only one. We predict a maximum compression ratio of 4.66 to occur for a temperature of 6.73 ×10 7 K. Finally we study how multiple shocks and ramp waves can be used to cover a large range of densities and temperatures. arXiv:2001.05300v1 [cond-mat.mtrl-sci]

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Section: Single and Multi Shock Hugoniot Curvessupporting

confidence: 77%

Magnesium oxide at extreme temperatures and pressures studied with first-principles simulations

Soubiran

González‐Cataldo

Driver

et al. 2019

The Journal of Chemical Physics

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“…At low to intermediate temperatures (T < 10 6 K), standard, orbital-based, Kohn-Sham DFT-MD is a suitable option to derive the EOS because it fully accounts the bonding effects and bound states within certain approximations of the exchange-correlation functional. However, the need to explicitly compute all partially occupied electronic orbitals causes DFT-MD to become computationally intractable beyond temperatures of roughly 10 6 K. Recent work on orbital-free DFT 48,50,60,61 and extended DFT-MD with free electron approximation for high energies 51 have made progress toward overcoming this difficulty, but their general applicability and accuracy needs to be further examined.…”

Section: Simulation Methodsmentioning

confidence: 99%

“…Recently, we have been developing PIMC for simulating heavier elements [46][47][48][52][53][54][55][56][57][58] , which is efficient at high temperatures, and can be used to complement DFT-MD calculations that are efficient at comparatively low temperatures. Combined data from PIMC and DFT-MD provide a coherent EOS over a wide density-temperature range that spans the condensed matter, WDM, and plasma regimes.…”

Section: Introductionmentioning

confidence: 99%

Equation of state and shock compression of warm dense sodium—A first-principles study

Zhang

Driver

Soubiran

et al. 2017

The Journal of Chemical Physics

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As one of the simple alkali metals, sodium has been of fundamental interest for shock physics experiments, but knowledge of its equation of state (EOS) in hot, dense regimes is not well known. By combining path integral Monte Carlo (PIMC) results for partially-ionized states [B. Militzer and K. P. Driver, Phys. Rev. Lett. 115, 176403 (2015)] at high temperatures and density functional theory molecular dynamics (DFT-MD) results at lower temperatures, we have constructed a coherent equation of state for sodium over a wide densitytemperature range of 1.93 − 11.60 g/cm 3 and 10 3 − 1.29 × 10 8 K. We find that a localized, Hartree-Fock nodal structure in PIMC yields pressures and internal energies that are consistent with DFT-MD at intermediate temperatures of 2×10 6 K. Since PIMC and DFT-MD provide a first-principles treatment of electron shell and excitation effects, we are able to identify two compression maxima in the shock Hugoniot curve corresponding to K-shell and L-shell ionization. Our Hugoniot curves provide a benchmark for widely-used EOS models, SESAME, LEOS, and Purgatorio. Due to the low ambient density, sodium has an unusually high first compression maximum along the shock Hugoniot curve. At beyond 10 7 K, we show that the radiation effect leads to very high compression along the Hugoniot curve, surpassing relativistic corrections, and observe an increasing deviation of the shock and particle velocities from a linear relation. We also compute the temperature-density dependence of thermal and pressure ionization processes.

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“…However, there are important limitations to their accuracy. OF-DFT replaces the orbital-based kinetic energy functional with a density-based TF functional and, therefore, is also unable to account for shell ionization effects [54]. On the other hand, DFT-based average atom methods only compute shell structure for an average ionic state and, subsequently, it is not well-suited for studies of compounds.…”

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confidence: 99%

First-principles equation of state and shock compression predictions of warm dense hydrocarbons

et al. 2017

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We use path integral Monte Carlo and density functional molecular dynamics to construct a coherent set of equation of state for a series of hydrocarbon materials with various C:H ratios (2:1, 1:1, 2:3, 1:2, and 1:4) over the range of 0.07 − 22.4 g cm −3 and 6.7 × 10 3 − 1.29 × 10 8 K. The shock Hugoniot curve derived for each material displays a single compression maximum corresponding to K-shell ionization. For C:H=1:1, the compression maximum occurs at 4.7-fold of the initial density and we show radiation effects significantly increase the shock compression ratio above 2 Gbar, surpassing relativistic effects. The single-peaked structure of the Hugoniot curves contrasts with previous work on higher-Z plasmas, which exhibit a two-peak structure corresponding to both K-and L-shell ionization. Analysis of the electronic density of states reveals that the change in Hugoniot structure is due to merging of the L-shell eigenstates in carbon, while they remain distinct for higher-Z elements. Finally, we show that the isobaric-isothermal linear mixing rule for carbon and hydrogen EOSs is a reasonable approximation with errors better than 1% for stellar-core conditions.Introduction. Hydrocarbon ablator materials are of primary importance for laser-driven shock experiments, such as those central to the study of inertial confinement fusion (ICF) [1][2][3] and the measurement of high energy density states relevant to giant planets [4] and stellar objects [5]. Accurate knowledge of the equation of state (EOS) of the hydrocarbon ablator is essential for optimizing experimental designs to achieve desired density and temperature states in a target. Consequently, a number of planar-driven shock wave experiments have been performed on hydrocarbon materials, including polystyrene (CH) [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23], glow-discharge polymer (GDP) [24][25][26][27][28], and foams [29][30][31][32], to measure the EOS. The highest pressure achieved among these experiments is 40 Mbar [14,15], which is yet not high enough to probe the effects of Kshell ionization on the shock Hugoniot curve. Since the first X-ray scattering results on CH at above 0.1 Gbar (1 Gbar=100 TPa) [33], ongoing, spherically-converging shock experiments using the Gbar platform at the National Ignition Facility (NIF) [34][35][36][37][38] and the OMEGA laser [39] will extend measurements of the shock Hugoniot curve of polystyrene to pressures above 0.35 Gbar and into the K-shell ionization regime [40].

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First-principles prediction of the softening of the silicon shock Hugoniot curve

Cited by 45 publications

References 69 publications

Magnesium oxide at extreme temperatures and pressures studied with first-principles simulations

Magnesium oxide at extreme temperatures and pressures studied with first-principles simulations

Equation of state and shock compression of warm dense sodium—A first-principles study

First-principles equation of state and shock compression predictions of warm dense hydrocarbons

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