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 M5: High Energy Density Physics/Warm Dense Matter I |
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Chair: Dawn Flicker, Sandia National Laboratories Room: Renaissance Ballroom D |
Wednesday, June 29, 2011 11:00AM - 11:30AM |
M5.00001: Molecular Dynamics of Hot Dense Plasmas: New Horizons Invited Speaker: We describe the status of a new time-dependent simulation capability for hot dense plasmas. The backbone of this multi-institutional computational and experimental effort---the Cimarron Project---is the massively parallel molecular dynamics (MD) code ``ddcMD''. The project's focus is material conditions such as exist in inertial confinement fusion experiments, and in many stellar interiors: high temperatures, high densities, significant electromagnetic fields, mixtures of high- and low-$Z$ elements, and non-Maxwellian particle distributions. Of particular importance is our ability to incorporate into this classical MD code key atomic, radiative, and nuclear processes, so that their interacting effects under non-ideal plasma conditions can be investigated. This talk summarizes progress in computational methodology, discusses strengths and weaknesses of quantum statistical potentials as effective interactions for MD, explains the model used for quantum events possibly occurring in a collision and highlights some significant results obtained to date. We will also discuss a new idea called kinetic theory MD which now being explored to deal more efficiently with the very disparate dynamical timescales that arise in fusion plasmas. We discuss how this approach can be derived rigorously from the n-body quantum Wigner equation and illustrate the approach with an example. [Preview Abstract] |
Wednesday, June 29, 2011 11:30AM - 11:45AM |
M5.00002: Equation of State of Shock Compressed Gases at Megabar Pressure Range Victor Gryaznov, Igor Iosilevskiy, Vladimir Fortov The model for equation of state of warm dense matter is developed in frames of ``chemical picture.'' Shock compressed gas is considered as a multi-component strongly interacted mixture of atoms, molecules, ions and electrons. Coulomb interaction of charged particles, short-range repulsion and attraction of heavy particles so as partial degeneracy of free electrons are taken into account. Contribution of repulsion of atoms and molecules to thermodynamic functions is considered in frames of extended soft-sphere model and corresponds to non-empirical atom-atomic approximation. The modified pseudopotential model is used for description of interaction of charged particles.The results of calculation of principal Hugoniots of hydrogen, deuterium and nitrogen together with calculation of thermodynamics for reshock states and third-shock reverberation are presented. The calculation results are compared with gas-gun, explosive, magnetically launched flyer-plate and laser experiments so as with the results of the first principle modeling. [Preview Abstract] |
Wednesday, June 29, 2011 11:45AM - 12:00PM |
M5.00003: Diffusion Monte Carlo calculations of Xenon and Krypton at High Pressure Luke Shulenburger, Thomas R. Mattsson Ab initio calculations based on density functional theory (DFT) have proven a valuable tool in understanding the properties of materials at extreme conditions. However, there are entire classes of materials where the current limitations of DFT cast doubt upon the predictive power of the method. These include so called strongly correlated systems and materials where van der Waals forces are important. Diffusion Monte Carlo (DMC) can treat materials with a different class of approximations that have generally proven to be more accurate. The use of DMC together with DFT may therefore improve the predictive capability of the ab initio calculation of materials at extreme conditions. We present two examples of this approach. In the first we use DMC total energies to address the discrepancy between DFT and diamond anvil cell melt curves of Xe.\footnote{Belonoshko el al. PRB {\bf 74}, 054114 (2006)} In the second, DMC is used to address the choice of density functional used in calculations of the Kr hugoniot. \\[4pt] 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. [Preview Abstract] |
Wednesday, June 29, 2011 12:00PM - 12:15PM |
M5.00004: Density functional theory simulations of polyethylene: principal Hugoniot, specific heats, compression and release isentropes K.R. Cochrane, M.P. Desjarlais, T.R. Mattsson An accurate equation of state (EOS) for polyethylene is required in order to model high energy density experiments for CH$_2$ densities above 1 g/cc, temperatures above 1~eV, and pressures above 1 Mbar. Density Functional Theory (DFT) based molecular dynamics has been established as a method capable of yielding high fidelity results for many materials at a wide range of pressures and temperatures and has recently been applied to complex polymers such as polyethylene [1]. Using high density polyethylene as the reference state, we compute the principal Hugoniot to 350 GPa, compression isentrope, and several release isentropes from states on the principal Hugoniot. We also calculate the specific heat and the dissociation along the Hugoniot. Our simulation results are validated by comparing to experimental data and then used to construct a wide range EOS. \noindent [1] T.R. Mattsson et al. Phys. Rev. B {\bf 81}, 054103 (2010). [Preview Abstract] |
Wednesday, June 29, 2011 12:15PM - 12:30PM |
M5.00005: Equation of State and Transport Data for Initially Wide Band Gap Materials from 0.1 to 10 Mbar Gilbert Collins, Ryan Rygg, Jon Eggert, Amy Lazicki, Damien Hicks, Peter Celliers, Paul Loubeyre, Stephanie Brygoo We present a suite of new shock compression data (pressure, temperature, density and reflectance) on originally large band-gap fluids including CO2 and Kr from 0.1 to 10 Mbar. Initial densities and pressures for these samples are tuned using diamond anvil cell containers. Shock data starting from initial cryogenic-liquid densities show insulator to conductor transitions at shock pressures less than 1 Mbar for Kr and near 2 Mbar for CO2. By comparing shock data at different initial densities we estimate the specific heat over the pressure range where significant ionization occurs. [Preview Abstract] |
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