Bulletin of the American Physical Society
15th APS Topical Conference on Shock Compression of Condensed Matter
Volume 52, Number 8
Sunday–Friday, June 24–29, 2007; Kohala Coast, Hawaii
Session G5: Equation of State II |
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Chair: Damien Hicks, Lawrence Livermore National Laboratory Room: Fairmont Orchid Hotel Plaza III |
Tuesday, June 26, 2007 10:30AM - 10:45AM |
G5.00001: Multiphase equation of state and strength properties of beryllium from ab initio and quantum molecular dynamics calculations Gregory Robert, Arnaud Sollier In the framework of density functional theory, static properties and phonons spectra of beryllium have been calculated under high compression (for pressures up to four Mbar) for two solids phases : hexagonal compact (hcp) and body-centred cubic (bcc). The melting curve and some isotherms in the liquid phase are calculated using quantum molecular dynamic. The coupling of these theoretical data to a quasi-harmonic approach (Debye model) for these three phases (two solids and a liquid) allows us to suggest a new theoretical phase diagram as well as a multiphase equation of state in a large range of pressure and temperature. The resulting 300K isotherm and Hugoniot curves as well as the evolution of the shear modulus with both pressure and temperature are in good agreement with available data. The elastic constants calculated under shock loading allow us to fit the coefficients of constitutive laws at very high pressures and high strain rates. [Preview Abstract] |
Tuesday, June 26, 2007 10:45AM - 11:00AM |
G5.00002: Hugoniot, shock melting and high pressure strength properties of beryllium Michael Desjarlais, Marcus Knudson, Raymond Lemke The shock melting of beryllium has gained interest of late due to its use as an ablator material in inertial confinement fusion capsules. Recently, experiments utilizing the flyer plate capability at the Sandia Z accelerator were performed to determine the Hugoniot and the shock melting properties of polycrystalline beryllium. Composite aluminum/copper flyer plates were used to shock load beryllium samples to pressures ranging from 1 to 4 Mbar. Multiple sample thicknesses allowed for the measurement of the release wave velocity, which is sensitive to the phase of the material in the shocked state. The release wave structure also provides estimates of material strength. Results of these experiments will be discussed and compared to detailed quantum molecular dynamics calculations which provide insight into the shock melting of beryllium and the extent of the coexistence region on the Hugoniot. [Preview Abstract] |
Tuesday, June 26, 2007 11:00AM - 11:15AM |
G5.00003: Multiphase Equation of State of Carbon at Extreme Conditions Lorin X. Benedict, Alfredo A. Correa, Eric R. Schwegler, David A. Young We describe our scheme to construct a multiphase EOS model for carbon at high pressures and temperatures. Three phases are considered: diamond, BC8, and liquid. Ab initio calculations of cold curves and phonon densities of states, as well as direct QMD computations of EOS are used to constrain simple analytic models for the free energies of the individual phases. Special care was taken to extract the anharmonic terms in the solid phases, and to compute their effect on the Hugoniot and phase lines. We discuss the challenges associated with using this information, together with experimental results, to produce an EOS table for use in hydro-code applications. [Preview Abstract] |
Tuesday, June 26, 2007 11:15AM - 11:30AM |
G5.00004: A new tabular EOS for hydrogen isotopes Didier Saumon The Saumon-Chabrier EOS model for hydrogen has been greatly improved, expanded to cover new physical regimes, and generalized to all three isotopes of hydrogen. The new table covers $4 \le T \le 10^9\,$K and $10^{-10} \le \rho \le 10^3\,$g/cm$^3$. At low temperatures, gaseous, liquid and solid molecular phases are included, as well as the monatomic solid plasma. The fluid phase is based on the chemical picture that describes interacting H$_2$, H, H$^+$ and electrons. Quantum corrections on the dense molecular, atomic and ionic fluids are included. The plasma model considers electron degeneracy, screening, relativistic effects, as well as strong plasma coupling. Interactions between charged and neutral particles have received particular attention as they control the pressure ionization of hydrogen. Notably, we found that previous predictions of a first order ``plasma phase transition" based on this type of model are inherent to their construction and are not credible. This new model does not predict such a transition. A brief overview of the model will be followed by extensive comparisons with static and dynamic compression data and ab initio simulations. [Preview Abstract] |
Tuesday, June 26, 2007 11:30AM - 11:45AM |
G5.00005: Multi--Phase Equation of State for Aluminum I.V. Lomonosov New experimental researches on shock [1] and isentropic [2] compression of aluminum at high pressures up to 500 GPa have demonstrated smooth monotonic dependencies without any anomalies. It results in more ``stiff'' compression curve and shock adiabat for aluminum that it was figured in previously. Adiabatic--expansion measurements of shocked aluminum [3] have brought new accurate data for the region of hot expanded liquid. Theoretical ``ab initio'' Quantum Molecular Dynamics calculations [4] in the region in the vicinity of the critical point established the reference domain of thermodynamic data. This complex of data serves as a fundament for a new multi--phase EOS for aluminum. It accounts for available to beginning of 2007 high pressure, high temperature experimental and theoretical data. Calculated thermodynamic functions describe the complete set of this information with high accuracy and reliability. The compression curve and the principal Hugoniot in developed EOS are fitted to new data [1-4], as well as the critical point. According to EOS, shocked aluminum melts at 113 GPa, the parameters of the critical point are: Pc=0.197 GPa, Tc=6250 K, Vc=1.423 g/cc. [1] M.D. Knudson et al., J. Appl. Phys., 94, 4420 (2003) [2] J.-P. Davis, J. Appl. Phys., 99, 103512 (2006) [3] M.D. Knudson, J.R. Asay, C. Deeney, J. Appl. Phys., 97, 073514 (2005) [4] M. P. Desjarlais, personal communication (2006). [Preview Abstract] |
Tuesday, June 26, 2007 11:45AM - 12:00PM |
G5.00006: Sound Velocity in Shock-Compressed Samples and Equation of State of Tin K.V. Khishchenko, V.E. Fortov, I.V. Lomonosov, M.V. Zhernokletov, A.E. Kovalev, A.B. Mezhevov, M.A. Mochalov, M.G. Novikov, A.N. Shuikin Equation of state for matter over a wide range of pressures and temperatures is required for simulations of processes in shock-compressed media. In the present study we have obtained data on the sound velocity behind the shock-wave front in tin at pressures $P \simeq 77\div 138$~GPa. In measurements we have used a shock and rarefaction overtake method with CCl$_4$ and C$_8$F$_{16}$ as the analyzer liquids. We propose a semiempirical equation of state for tin with taking into account the polymorphs transformation, melting, and evaporation effects. Calculation results are compared with the newly acquired and available experimental data at high energy densities. The multi-phase equation of state obtained can be used efficiently in modeling of physical phenomena at high dynamic pressures. [Preview Abstract] |
Tuesday, June 26, 2007 12:00PM - 12:15PM |
G5.00007: Tabular Multiphase Equations of State for Metals and Their Applications Pavel Levashov, Konstantin Khishchenko In this work we use multiphase equations of state in tabular form for numerical simulation of different problems of shock-wave physics. These equations of state take into account melting, evaporation and sublimation phase transitions and can be applied in metastable regions including those under negative pressure. We use two interpolation techniques for calculation of thermodynamic properties: (i) adaptation of a rectangular grid to phase and metastable boundaries and (ii) triangular grid in every region of phase diagram. Both techniques allow one to unambiguously determine the phase state of a given point of phase diagram. For very fast processes different temperatures for ions and electrons can be used. Several applications of multiphase equations of state will be presented: simulation of the initial stage of electrical explosion of metal wires and foils, hypervelocity impact, interaction of intense laser pulses with matter etc. Information about phase state in every point of the flux allows us to study phase transition waves, apply different destruction criteria and analyse processes in metastable regions. The work is done under RFBR financial support, grant 06-02-17464. [Preview Abstract] |
Tuesday, June 26, 2007 12:15PM - 12:30PM |
G5.00008: Hugoniot measurement of RbCl single crystal Takahiro Kinoshita, Takayuki Inoue, Yuyang Zhang, Tsutomu Mashimo The B1-B2 phase transition of Rubidium chloride (RbCl) was reported under hydrostatic compression by diamond anvil cell. However, the mechanism of phase transition and equation of states (EOS) have been unknown. Hugoniot-measurement experiments were performed on RbCl single crystals by means of the inclined-mirror method combined with propellant guns to study the B1-B2 phase transition and EOS. A kink was found on the measured Hugoniot curve. The EOS of the high-pressure phase will be discussed. MD simulation studies were also performed to discuss the mechanism of B1-B2 phase transition. [Preview Abstract] |
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