We present a 5-phase equation of state (EOS) for elemental carbon. The phases considered are: diamond, BC8, simple-cubic, simple-hexagonal, and the liquid/plasma state. solid phase free energies are constrained by density functional theory (DFT) calculations. Vibrational contributions to energy each treated within quasiharmonic framework. liquid model is fitting combination DFT molecular dynamics performed over range 10,000 K < T 100,000 K, path integral quantum Monte Carlo calculations >...

We develop an all-electron path integral Monte Carlo method with free-particle nodes for warm dense matter and apply it to water carbon plasmas. thereby extend studies beyond hydrogen helium elements core electrons. Path results pressures, internal energies, pair-correlation functions compare well density functional theory molecular dynamics calculations at temperatures of (2.5-7.5)×10(5) K, both methods together form a coherent equation state over density-temperature range 3-12 g/cm(3)...

We put together a first-principles equation of state (FPEOS) database for matter at extreme conditions by combining results from path integral Monte Carlo and density functional molecular dynamics simulations the elements H, He, B, C, N, O, Ne, Na, Mg, Al, Si as well compounds $\mathrm{LiF}, {\mathrm{B}}_{4}\mathrm{C}, \mathrm{BN}, {\mathrm{CH}}_{4}, {\mathrm{CH}}_{2}, {\mathrm{C}}_{2}{\mathrm{H}}_{3}, \mathrm{CH}, {\mathrm{C}}_{2}\mathrm{H}, \mathrm{MgO}, \mathrm{and} {\mathrm{MgSiO}}_{3}$....

We extend the applicability range of fermionic path integral Monte Carlo simulations to heavier elements and lower temperatures by introducing various localized nodal surfaces. Hartree-Fock nodes yield most accurate prediction for pressure internal energy, which we combine with results from density functional molecular dynamics obtain a consistent equation state hot, dense silicon under plasma conditions in regime warm matter (2.3-18.6 g cm(-3), 5.0×10(5)-1.3×10(8) K). The shock Hugoniot...

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 state (EOS) simulations cover a wide density-temperature range 0.1-32.4gcm^{-3} 10^{4}-10^{8} K. Since PIMC DFT-MD accurately treat effects the atomic shell structure, we find two compression maxima along principal Hugoniot curve attributed K-shell L-shell ionization. The results provide benchmark for...

Using path integral Monte Carlo (PIMC) and density functional molecular dynamics (DFT-MD) simulation methods, we compute a coherent equation of state (EOS) nitrogen that spans the liquid, warm dense matter (WDM), plasma regimes. Simulations cover wide range density-temperature space, $1.5--13.9\phantom{\rule{4pt}{0ex}}\mathrm{g}{\mathrm{cm}}^{\ensuremath{-}3}$ ${10}^{3}--{10}^{9}$ K. In dissociation regime, extend pressure-temperature phase diagram beyond previous studies, providing Hugoniot...

Silicon undergoes a phase transition from the semiconducting diamond to metallic $\ensuremath{\beta}\text{-Sn}$ under pressure. We use quantum Monte Carlo calculations predict transformation pressure and compare results density-functional employing local-density approximation, generalized-gradient approximations PBE, PW91, WC, AM05, PBEsol, hybrid functional HSE06 for exchange-correlation functional. Diffusion predicts of $14.0\ifmmode\pm\else\textpm\fi{}1.0\text{ }\text{GPa}$ slightly above...

All-electron path integral Monte Carlo (PIMC) and density functional theory molecular dynamics (DFT-MD) simulations provide a consistent, first-principles investigation of warm dense neon plasmas in the density-temperature range 1--15 g ${\mathrm{cm}}^{\ensuremath{-}3}$ ${10}^{4}--{10}^{9}$ K. At high temperatures, DFT-MD becomes intractable because too many partially occupied bands, while at lower PIMC is free-particle approximation fermion nodes. In combination, pressures internal energies...

We use path integral Monte Carlo and density functional molecular dynamics to construct a coherent set of equations state (EOS) for series hydrocarbon materials with various C:H ratios (2:1, 1:1, 2:3, 1:2, 1:4) over the range 0.07-22.4gcm^{-3} 6.7×10^{3}-1.29×10^{8}K. The shock Hugoniot curve derived each material displays single compression maximum corresponding K-shell ionization. For = occurs at 4.7-fold initial we show radiation effects significantly increase ratio above 2 Gbar,...

We perform all-electron path integral Monte Carlo (PIMC) and density functional theory molecular dynamics (DFT-MD) calculations to explore warm dense matter states of oxygen. Our simulations cover a wide density-temperature range 1–100 g cm−3 104–109 K. By combining results from PIMC DFT-MD, we are able compute pressures internal energies first-principles at all temperatures provide coherent equation state. compare our with analytic equations state, which tend agree for above 8 × 106...

Shock compression of silicon (Si) under extremely high pressures (>100 Mbar) was investigated by using two first-principles methods orbital-free molecular dynamics (OFMD) and path integral Monte Carlo (PIMC). While from the agree very well, PIMC predicts a second maximum because 1s electron ionization that is absent in OFMD calculations since Thomas-Fermi-based theories lack shell structure. The Kohn-Sham density functional theory used to calculate equation state (EOS) warm dense for...

Quantitative, nanometer-scale spatial resolution electron energy-loss spectroscopy (EELS) was used to map the composition of coherent islands grown by molecular-beam epitaxy pure Ge onto Si(100). The concentration XGe decreased, and Ge/Si interface became more diffuse as growth temperature increased from 400 700 °C. Integrated island volumes measured atomic force microscopy (AFM) linearly with coverage θGe, slopes greater than 1. This result confirmed that is faster deposition rate due Si...

Carbon-hydrogen plasmas and hydrocarbon materials are of broad interest to laser shock experimentalists, high energy density physicists, astrophysicists. Accurate equations state (EOSs) hydrocarbons valuable for various studies from inertial confinement fusion planetary science. By combining path integral Monte Carlo (PIMC) results at temperatures functional theory molecular dynamics lower temperatures, we compute the EOSs simulations performed 1473 separate (ρ, T)-points distributed over a...

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 LiF. Our simulations cover a wide density-temperature range $2.08-15.70$~g$\,$cm$^{-3}$ $10^4-10^9$~K. Since PIMC DFT-MD accurately treat effects atomic shell structure, we find pronounced compression maximum shoulder on the principal Hugoniot curve attributed K-shell L-shell ionization. The results provide benchmark for...

Recent observations of Jupiter and Saturn provided by spacecraft missions, such as Juno Cassini, compel us to revise improve our models giant planet interiors. Even though hydrogen helium are far the dominant species in these planets, heavy elements can play a significant role structure evolution planet. For instance, giant-planet cores may be eroded their surrounding fluid, which would result significantly increased concentration hydrogen-helium envelope. Furthermore, could inhibit...

As one of the simple alkali metals, sodium has been fundamental interest for shock physics experiments, but knowledge its equation state (EOS) in hot, dense regimes is not well known. By combining path integral Monte Carlo (PIMC) results partially ionized states [B. Militzer and K. P. Driver, Phys. Rev. Lett. 115, 176403 (2015)] at high temperatures density functional theory molecular dynamics (DFT-MD) lower temperatures, we have constructed a coherent over wide density-temperature range...

Water and hydrogen at high pressure make up a substantial fraction of the interiors giant planets. Using ab initio random structure search methods we investigate ground-state crystal structures water, hydrogen, hydrogen-oxygen compounds. We find that, pressures beyond 14 Mbar, excess is incorporated into ice phase to form novel with H4O stoichiometry. also predict two new ground state structures, P2_1/m I4/mmm, for post-C2/m water ice.

Triple bonding in the nitrogen molecule (N_{2}) is among strongest chemical bonds with a dissociation enthalpy of 9.8 eV/molecule. Nitrogen therefore an excellent test bed for theoretical and numerical methods aimed at understanding how evolves under influence extreme pressures temperatures warm dense matter regime. Here, we report laser-driven shock experiments on fluid molecular up to 800 GPa 4.0 g/cm^{3}. Line-imaging velocimetry measurements impedance matching method quartz reference...

An experiment to determine the Brewster angle and study polarization of reflected light is discussed in this paper. The equipment used commercially available from PASCO Scientific. A sensor, which detects intensity light, connected a computer through Pasco Science Workshop 750 interface read directly digital meter program. Intensities polarized plane incidence perpendicular were obtained as function incidence. results are consistent with Fresnel’s laws reflection. In addition, refractive...

We have performed quantum Monte Carlo (QMC) simulations and density functional theory (DFT) calculations to study the equations of state MgSiO$_3$ perovskite (Pv) post-perovskite (PPv), up pressure temperature conditions base Earth's lower mantle. The ground energies were derived using QMC dependent Helmholtz free calculated within quasi-harmonic approximation perturbation theory. for both phases agree well with experiments, better than those from generalized gradient (GGA) calculations....

Atomic force microscopy, transmission electron and energy-loss spectroscopy have been used to study the size, structure, composition of Ge/Si(100) islands grown by molecular beam epitaxy at 700 °C. It is found that island evolution qualitatively different than for growth lower substrate temperatures. For 1.4 ML/min, determined be Si0.56Ge0.44 appears independent size. A higher rate, 4.8 kinetically stabilizes pure Ge pyramids prior Si interdiffusion taking place. These clusters are absent...

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 uncertain how much heating occurs under these shock-free conditions. Here, we performed a series ab initio simulations on carbon order to match the density-stress measurements Smith et al. [Smith al., Nature (London) 511, 330 (2014)]. We considered isotropically as...

We combine two first-principles computer simulation techniques, path integral Monte Carlo and density functional theory molecular dynamics, to determine the equation of state magnesium oxide in regime warm dense matter, with densities ranging from 0.35 71 g cm-3 temperatures 10 000 K 5 × 108 K. These conditions are relevant for interiors giant planets stars as well shock wave compression measurements inertial confinement fusion experiments. study electronic structure MgO ionization...