Bulletin of the American Physical Society
20th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 62, Number 9
Sunday–Friday, July 9–14, 2017; St. Louis, Missouri
Session T6: Equation of State V |
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Chair: Damian Swift, Lawrence Livermore National Laboratory Room: Regency Ballroom E |
Thursday, July 13, 2017 11:15AM - 11:30AM |
T6.00001: A multiphase iron equation of state Travis Sjostrom, Scott Crockett We detail a new extended range multiphase equation of state for iron. Particular attention is paid to the warm dense liquid regime where we have performed density functional theory (DFT) based quantum molecular dynamics for densities up to 30 g/cm$^3$ and temperatures from 1 to 100 eV. Additionally we make use of DFT results to constrain the EOS for thermally excited solids phases and the melt curve. Significant comparisons are made with experimental data and distinction is made between the accuracies of the simulation and experimental data. [Preview Abstract] |
Thursday, July 13, 2017 11:30AM - 11:45AM |
T6.00002: Hugoniot Measurements of Silicon Shock Compressed to 25 Mbar Brian Henderson, Danae Polsin, Tom Boehly, Michelle Gregor, Suxing Hu, Gilbert Collins, Ryan Rygg, Dayne Fratanduono, Peter Celliers We present results of laser-driven shock experiments that compressed silicon samples to 25 Mbar. Impedance matching to a quartz reference provided Hugoniot data. Since silicon is opaque, a quartz witness was placed adjacent to the silicon samples; this afforded the use of the unsteady wave correction\cite{Fratanduono:1}to increase the precision of the transit-time measurements of shock velocity. Results are compared with both \textit{SESAME} tables and quantum molecular dynamics calculations. This material is based upon work supported by the Department Of Energy National Nuclear Security Administration under Award Number DENA0001944. D. E. Fratanduono \textit{et al}., J. Appl. Phys. \textbf{116}, 033517 (2104). [Preview Abstract] |
Thursday, July 13, 2017 11:45AM - 12:00PM |
T6.00003: Calculation of entropy in classical and first-principles molecular dynamics simulation Dmitry Minakov, Pavel Levashov Theoretical determination of solid-liquid phase boundaries is a long–standing problem in physics. Direct reconstruction of melting curves based on the equality of Gibbs energy for both phases sets a complicated task of entropy calculation, that remains the major impediment of this method. We present a detailed analysis of entropy reconstruction from a velocity autocorrelation function in molecular dynamics simulation for solid and liquid states. The reconstruction is based on the vibrational density of states (VDOS) and for the liquid phase is known as a two-phase thermodynamic (2PT) model. We compare this method with more complicated technique of thermodynamic integration and the Widom’s particle insertion method. We also present results of \textit{ab initio} calculations of melting curve and release isentropes using 2PT model for various metals. [Preview Abstract] |
Thursday, July 13, 2017 12:00PM - 12:15PM |
T6.00004: The Shock and Release Behaviors of Diamond at Terapascal Pressures Michelle Gregor, Dayne Fratanduono, Peter Celliers, Tom Braun, Jon Eggert, Danae Polsin, Andrew Sorce, Ryan Rygg, Gilbert Collins, Thomas Boehly, Chad McCoy, David Meyerhofer The behavior of carbon at terapascal pressures is important to modeling ice giants and white dwarf stars and to designing inertial confinement fusion (ICF) experiments, where diamond is used to contain and compress the hydrogen fuel. We report on experiments using the OMEGA laser that shock compressed diamond to 26 Mbar. The shocked diamond released into standard materials with known Hugoniots (quartz, silica foam, liquid deuterium, and polystyrene). Hugoniot and release data were obtained for both single-crystal diamond (SCD) and nanocrystalline diamond (NCD), which is comprised of nanometer-scale diamond grains and is $\sim$5\% less dense than SCD. We find that the NCD used in ICF experiments has a stiffer Hugoniot than SCD that can be attributed to porosity. A Gr\"{u}neisen parameter of $\sim$1 for high-pressure fluid carbon was derived from the NCD and SCD Hugoniots and is used in Mie-Gr\"{u}neisen models to accurately describe the NCD and SCD release data. [Preview Abstract] |
Thursday, July 13, 2017 12:15PM - 12:45PM |
T6.00005: Shock-and-Release to the Liquid-Vapor Phase Boundary: Experiments and Applications to Planetary Science Invited Speaker: Sarah Stewart Shock-induced vaporization was a common process during the end stages of terrestrial planet formation and transient features in extra-solar systems are attributed to recent giant impacts. At the Sandia Z Machine, my collaborators and I are conducting experiments to study the shock Hugoniot and release to the liquid-vapor phase boundary of major minerals in rocky planets. Current work on forsterite, enstatite and bronzite and previous results on silica, iron and periclase demonstrate that shock-induced vaporization played a larger role during planet formation than previously thought. I will provide an overview of the experimental results and describe how the data have changed our views of planetary impact events in our solar system and beyond. \\ \\ Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract No. DE-AC04-94AL85000. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. This work is supported by the Z Fundamental Science Program at Sandia National Laboratories, DOE-NNSA grant DE- NA0002937, NASA grant \# NNX15AH54G, and UC Multicampus-National Lab Collaborative Research and Training grant \#LFR-17-449059. [Preview Abstract] |
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