First-principles equation of state calculations of warm dense nitrogen

Driver, Kevin P.; Militzer, Burkhard

doi:10.1103/physrevb.93.064101

Cited by 65 publications

(46 citation statements)

References 100 publications

(151 reference statements)

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“…The inclusion of permutation space results in inefficient sampling for lower temperatures since the positive and negative contributions to the integration are nearly cancelled out. This fermion sign problem [50] was overcome by restricting the paths using free-particle nodes or variational density-matrix nodes [51], which has succeeded in making PIMC simulations feasible to reach the lower temperatures of [56], carbon [57], water [58], neon [59], nitrogen [60], and oxygen [61].…”

Section: Pimcmentioning

confidence: 99%

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

Militzer

Collins

et al. 2016

Phys. Rev. B

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Shock compression of silicon (Si) under extremely high pressures (>100 Mbar) was investigated by using two first-principles methods of orbital-free molecular dynamics (OFMD) and path integral Monte Carlo (PIMC). While pressures from the two methods agree very well, PIMC predicts a second compression maximum because of 1s electron ionization that is absent in OFMD calculations since Thomas-Fermi-based theories lack shell structure. The Kohn-Sham density functional theory is used to calculate the equation of state (EOS) of warm dense silicon for low-pressure loadings (P < 100 Mbar).Combining these first-principles EOS results, the principal shock Hugoniot curve of 2 silicon for pressures varying from ~1 Mbar to above ~10 Gbar was derived. We find that silicon is ~20% or more softer than what was predicted by widely-used EOS models.Existing high-pressure experimental data (P ≈ 1 − 2 Mbar) seem to indicate this softening behavior of Si, which calls for future strong-shock experiments (P > 10 Mbar) to benchmark our results.

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Section: Pimcmentioning

confidence: 99%

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

Militzer

Collins

et al. 2016

Phys. Rev. B

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“…NPA successfully predicts the S(k) and g(r), inclusive of pre-peaks due to C-C bonding [20] as also obtained from DFT+MD simulations of WDM-carbon [18,19]. The NPA and Path Integral Monte Carlo g(r) [43] also agree closely [20]. No experimental σ ib are available; hence we calculate only σ ic and σ uf to display the remarkable difference in the conductivities of complex WDMs with (transient) covalent bonding, compared to simpler WDMs like Al and Li.…”

Section: The Conductivities Of Wdm Carbonmentioning

confidence: 99%

Isochoric, isobaric, and ultrafast conductivities of aluminum, lithium, and carbon in the warm dense matter regime

et al. 2017

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We study the conductivities σ of (i) the equilibrium isochoric state (σis), (ii) the equilibrium isobaric state (σ ib ), and also the (iii) non-equilibrium ultrafast matter (UFM) state (σ uf ) with the ion temperature Ti less than the the electron temperature Te. Aluminum, lithium and carbon are considered, being increasingly complex warm dense matter (WDM) systems, with carbon having transient covalent bonds. First-principles calculations, i.e., neutral-pseudoatom (NPA) calculations and density-functional theory (DFT) with molecular-dynamics (MD) simulations, are compared where possible with experimental data to characterize σic, σ ib and σ uf . The NPA σ ib are closest to the available experimental data when compared to results from DFT+MD, where simulations of about 64-125 atoms are typically used. The published conductivities for Li are reviewed and the value at a temperature of 4.5 eV is examined using supporting X-ray Thomson scattering calculations. A physical picture of the variations of σ with temperature and density applicable to these materials is given. The insensitivity of σ to Te below 10 eV for carbon, compared to Al and Li, is clarified.

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“…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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First-principles equation of state calculations of warm dense nitrogen

Cited by 65 publications

References 100 publications

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

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

Isochoric, isobaric, and ultrafast conductivities of aluminum, lithium, and carbon in the warm dense matter regime

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

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