Bulletin of the American Physical Society
17th Biennial International Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 56, Number 6
Sunday–Friday, June 26–July 1 2011; Chicago, Illinois
Session U6: Equation of State III |
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Chair: Heath Hanshaw, Sandia National Laboratories Room: Grand Ballroom VI |
Thursday, June 30, 2011 2:00PM - 2:15PM |
U6.00001: A Relatively Simple Analytical Equation of State for Liquid Metals John Maw Over the past 50 years considerable research has been carried out in attempts to model the behaviour of liquid metals. Many methods have been proposed for estimating the critical point properties and a number of equations of state (EOS) have been developed, usually in tabular form, to describe the liquid vapour transition in a range of metals. In this paper a previously described analytical EOS form has been extended to provide a simple treatment of the liquid/vapour phases of metals. This has the advantage over tabular forms that it can be easily modified to assess the sensitivity of simulations to uncertainties in the EOS or to take into account new experimental data. The steps involved in determining the EOS parameters are described and comparisons are made with experimental data and other EOS models for a number of metals. [Preview Abstract] |
Thursday, June 30, 2011 2:15PM - 2:30PM |
U6.00002: Resolving the Shock Wave Profile in Viscous Fluids Kenneth Jordan, John Borg Capturing and modeling shock wave profiles has a long history in computational analysis. Often artificial irreversibilities and/or smearing schemes are implemented in order to stabilize and resolve the shock. This work presents a direct numeric simulation of the full Navier-Stokes equations where the shock profile is completely resolved without the use of artificial viscosity or shock smearing techniques. Several viscosity models are employed to study the role of viscosity on this second order accurate finite difference scheme. The results are compared to an analytic solutions and experimental results. The results indicated that the shock front thickness and entropy production are in good agreement with simple analytic solutions and experimental results. The extension of this technique to solid and granular materials will be discussed. [Preview Abstract] |
Thursday, June 30, 2011 2:30PM - 2:45PM |
U6.00003: Volume dependence of the transit contribution in the vibration-transit theory of liquids Eric Chisolm, Nicolas Bock, Duane Wallace Previously, we created a model for the transit contribution to the thermodynamic functions of a liquid [Phys.\ Rev.\ \textbf{E} 81, 041201 (2010)]. The model modifies the potential surface in which atoms in the liquid state move. The two parameters of the model are $\chi$, the maximum transit entropy, and $\theta_{\rm tr}$, a characteristic temperature near (but not equal to) the melt temperature. Using a combination of experimental data and density functional theory results, we calculate the volume derivatives of these parameters, thus giving the first-order volume dependence of the model. [Preview Abstract] |
Thursday, June 30, 2011 2:45PM - 3:00PM |
U6.00004: Equation-of-state measurements of laser-shocked liquid hydrogen Takayoshi Sano, Norimasa Ozaki, Tatsuhiro Sakaiya, Keisuke Shigemori, Masahiro Ikoma The properties of hydrogen at high pressure and high density are of great scientific interest. The equation of state (EOS) of hydrogen at these conditions is essential for modeling of the interior structure of gas giant planets. The large diversity in the estimation of Jupiter's core mass is resulted from the uncertainty in the EOS data especially in the region around the insulator-to-metal transition. Chemical free-energy models and ab initio simulations have been used to predict the properties of warm dense hydrogen, but the results vary widely and have not converged yet. Therefore, accurate experimental data for the hydrogen EOS are required for evaluation of the theoretical models. In this work, the principal Hugoniot for liquid hydrogen was obtained up to 55 GPa under laser-driven shock loading. The pressure and density of compressed hydrogen were determined by impedance-matching to a quartz standard. The shock temperature was independently measured from the brightness of the shock front. Hugoniot data of hydrogen provide a good benchmark to modern theories of condensed matter. The initial number density of liquid hydrogen is lower than that for liquid deuterium, and this results in shock compressed hydrogen having a higher compression and higher temperature than deuterium at the same shock pressure. [Preview Abstract] |
Thursday, June 30, 2011 3:00PM - 3:15PM |
U6.00005: The Liquid Krypton Hugoniot at Megabar Pressures Seth Root, Rudy J. Magyar, Ann E. Mattsson, David L. Hanson, Thomas R. Mattsson Krypton is an ideal candidate to study multi-Mbar pressure effects on elements with filled-shell electron configurations. Few experimental data on Kr at high pressures exist, however, with prior Hugoniot data limited to below 1 Mbar. Similar to liquid xenon [1], the current Kr equation of state (EOS) models agree with the data and each other below 1 Mbar, but diverge with increasing pressure. We examine the liquid Kr Hugoniot up to 8 Mbar by using density functional theory (DFT) methods and by performing shock compression experiments on the Sandia Z -- accelerator. Our initial DFT Kr Hugoniot calculations indicated the standard PAW potential is inadequate at the high pressures and temperatures occurring under strong shock compression. A new Kr PAW potential was constructed giving improved scattering properties of the atom at high energies. The Z Hugoniot measurements above 1 Mbar validated the DFT results and the pseudo-potential. The DFT and Z results suggest that the current EOS models require some modifications. [1] S. Root \textit{et al}., PRL, \textbf{105}, 085501 (2010). Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U. S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. [Preview Abstract] |
Thursday, June 30, 2011 3:15PM - 3:30PM |
U6.00006: Shock compression of CO2: experiments on Z and first-principles simulations T.R. Mattsson, S. Root, L. Shulenburger, K.R. Cochrane The principal Hugoniot for CO2 is known up to 75 GPa and it displays a plateau in shock pressure interpreted as the result of dissociation [1]. To confidently model the structure of gas-giant planets and the deep carbon cycle of the earth it is important to accurately know the properties of CO2 at even higher pressures. We present results from flyer-plate experiments on Sandia's Z-machine providing data for CO2 between 150 and 600 GPa. We also present Density Functional Theory (DFT) based simulations up to 500 GPa, including a chemical composition analysis. Quantum Monte Carlo (QMC) is applied to assess the accuracy of exchange-correlation functionals. We conclude that the plateau in shock pressure at 50 GPa [1] is consistent with dissociation. Beyond 3.5 g/cm$^3$ density, the shock pressure raises rapidly due to completed dissociation.\\[4pt] [1] W. Nellis, et. al. , J. Chem. Phys. {\bf 95}, 5268 (1991). [Preview Abstract] |
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