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AIP Conference Proceedings
Cochrane, Kyle R.; Desjarlais, Michael P. ; Mattsson, Thomas M.
An accurate equation of state (EOS) for polyethylene is required in order to model high energy density experiments for CH2 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 [2, 3] and then used to construct a wide range EOS. © 2012 American Institute of Physics.
AIP Conference Proceedings
Thompson, Aidan P. ; Lane, James M. ; Desjarlais, Michael P.
The response of beryllium to dynamic loading has been extensively studied, both experimentally and theoretically, due to its importance in several technological areas. We use a MEAM empirical potential to examine the melt transition. MD simulations of equilibrated two-phase systems were used to calculate the HCP melting curve up to 300 GPa. This was found to agree well with previous ab initio calculations. The Hugoniostat method was used to examine dynamic compression along the two principal orientations of the HCP crystal. In both directions, the melting transition occurred at 230 GPa and 5000 K, consistent with the equilibrium melting curve. Direct NEMD simulations of uniaxial compression show a transition to an amorphous material at shocked states that lie below the equilibrium melt curve. © 2012 American Institute of Physics.
AIP Conference Proceedings
Hanshaw, Heath L. ; Knudson, Marcus D. ; Martin, Matthew ; Desjarlais, Michael P. ; Lemke, Raymond W.
The double shock layered high-velocity flyer plate is one new capability being developed on Sandia's Z machine. With this technique, dynamic material data at high energy densities can be obtained at points in phase space which lie neither on principal Hugoniots nor on quasi-isentropic ramp curves. We discuss the double shock capability development experiments being performed on Z. © 2012 American Institute of Physics.
Ao, Tommy A. ; Bailey, James E. ; Hansen, Stephanie B. ; Desjarlais, Michael P. ; Sinars, Daniel S. ; Smith, Ian C.
Shulenburger, Luke N. ; Root, Seth R. ; Cochrane, Kyle C. ; Desjarlais, Michael P. ; Mattsson, Thomas M. ; Flicker, Dawn G.
Matzen, M.K. ; Mazarakis, Michael G. ; Bailar, James M. ; Cuneo, M.E. ; Desjarlais, Michael P. ; Glover, Steven F.
Ao, Tommy A. ; Harding, Eric H. ; Bailey, James E. ; Sinars, Daniel S. ; Desjarlais, Michael P. ; Hansen, Stephanie B. ; Lemke, Raymond W. ; Smith, Ian C.
Ao, Tommy A. ; Bailey, James E. ; Hansen, Stephanie B. ; Desjarlais, Michael P. ; Mix, L.P. ; Smith, Ian C. ; Sinars, Daniel S.
Nature
Knudson, Marcus D. ; Desjarlais, Michael P. ; Mattsson, Thomas M.
Mattsson, Thomas M. ; Knudson, Marcus D. ; Desjarlais, Michael P.
Knapp, Patrick K. ; Sinars, Daniel S. ; Desjarlais, Michael P.
Mattsson, Thomas M. ; Desjarlais, Michael P.
Lane, James M. ; Grest, Gary S. ; Thompson, Aidan P. ; Desjarlais, Michael P. ; Mattsson, Thomas M.
Desjarlais, Michael P.
Knudson, Marcus D. ; Desjarlais, Michael P.
Ao, Tommy A. ; Wenger, D.F. ; Bailey, James E. ; Desjarlais, Michael P. ; Hansen, Stephanie B. ; Knudson, Marcus D. ; Lemke, Raymond W. ; Mix, L.P. ; Sinars, Daniel S. ; Smith, Ian C.
Hansen, Stephanie B. ; Desjarlais, Michael P. ; Bailey, James E. ; Harding, Eric H. ; Ao, Tommy A.
Ao, Tommy A. ; Wenger, D.F. ; Bailey, James E. ; Desjarlais, Michael P. ; Hansen, Stephanie B. ; Knudson, Marcus D. ; Lemke, Raymond W. ; Mix, L.P. ; Sinars, Daniel S. ; Smith, Ian C.
Mattsson, Thomas M. ; Desjarlais, Michael P. ; Wills, Ann E.
Root, Seth R. ; Knudson, Marcus D. ; Desjarlais, Michael P. ; Mattsson, Thomas M.
Knudson, Marcus D. ; Mattsson, Thomas M. ; Desjarlais, Michael P.
Mattsson, Thomas M. ; Desjarlais, Michael P.
Sears, Mark P. ; Wills, Ann E. ; Desjarlais, Michael P. ; Modine, N.A. ; Wright, Alan F. ; Muller, Richard P.
Knudson, Marcus D. ; Desjarlais, Michael P.
Location of the liquid-vapor critical point (c.p.) is one of the key features of equation of state models used in simulating high energy density physics and pulsed power experiments. For example, material behavior in the location of the vapor dome is critical in determining how and when coronal plasmas form in expanding wires. Transport properties, such as conductivity and opacity, can vary an order of magnitude depending on whether the state of the material is inside or outside of the vapor dome. Due to the difficulty in experimentally producing states near the vapor dome, for all but a few materials, such as Cesium and Mercury, the uncertainty in the location of the c.p. is of order 100%. These states of interest can be produced on Z through high-velocity shock and release experiments. For example, it is estimated that release adiabats from {approx}1000 GPa in aluminum would skirt the vapor dome allowing estimates of the c.p. to be made. This is within the reach of Z experiments (flyer plate velocity of {approx}30 km/s). Recent high-fidelity EOS models and hydrocode simulations suggest that the dynamic two-phase flow behavior observed in initial scoping experiments can be reproduced, providing a link between theory and experiment. Experimental identification of the c.p. in aluminum would represent the first measurement of its kind in a dynamic experiment. Furthermore, once the c.p. has been experimentally determined it should be possible to probe the electrical conductivity, opacity, reflectivity, etc. of the material near the vapor dome, using a variety of diagnostics. We propose a combined experimental and theoretical investigation with the initial emphasis on aluminum.
Knudson, Marcus D. ; Desjarlais, Michael P.
Physical Review Letters
Lemke, R.W.; Sinars, Daniel S. ; Waisman, E.M.; Cuneo, M.E. ; Yu, E.P.; Haill, Thomas A. ; Hanshaw, Heath L. ; Brunner, Thomas A. ; Jennings, C.A.; Stygar, William A. ; Desjarlais, Michael P. ; Mehlhorn, Thomas A. ; Porter, J.L.
X-ray production by imploding wire-array Z pinches is studied using radiation magnetohydrodynamics simulation. It is found that the density distribution created by ablating wire material influences both x-ray power production, and how the peak power scales with applied current. For a given array there is an optimum ablation rate that maximizes the peak x-ray power, and produces the strongest scaling of peak power with peak current. This work is consistent with trends in wire-array Z pinch x-ray power scaling experiments on the Z accelerator. © 2009 The American Physical Society.
Physics of Plasmas
Yu, Edmund Y. ; Cuneo, M.E. ; Desjarlais, Michael P. ; Lemke, Raymond W. ; Sinars, Daniel S. ; Haill, Thomas A. ; Waisman, E.M.; Bennett, G.R.; Jennings, C.A.; Mehlhorn, T.A.; Brunner, T.A.; Hanshaw, H.L.; Porter, J.L.; Stygar, W.A.; Rudakov, L.I.
The implosion phase of a wire-array Z pinch is investigated using three-dimensional (3D) simulations, which model the mass ablation phase and its associated axial instability using a mass injection boundary condition. The physical mechanisms driving the trailing mass network are explored, and it is found that in 3D the current paths though the trailing mass can reduce bubble growth on the imploding plasma sheath, relative to the 2D (r,z) equivalent. Comparison between the simulations and a high quality set of experimental radiographs is presented. © 2008 American Institute of Physics.
Lemke, Raymond W. ; Sinars, Daniel S. ; Yu, Edmund Y. ; Haill, Thomas A. ; Brunner, Thomas A. ; Hanshaw, Heath L. ; Cuneo, M.E. ; Desjarlais, Michael P. ; Mehlhorn, Thomas A.
Mattsson, Thomas M. ; Desjarlais, Michael P. ; Knudson, Marcus D.
Desjarlais, Michael P. ; Vogler, Tracy V.
Carpenter, John H. ; Desjarlais, Michael P. ; Wills, Ann E.
Lemke, Raymond W. ; Haill, Thomas A. ; Yu, Edmund Y. ; Sinars, Daniel S. ; Hanshaw, Heath L. ; Brunner, Thomas A. ; Cuneo, M.E. ; Desjarlais, Michael P. ; Mehlhorn, Thomas A.
Desjarlais, Michael P. ; Dolan, Daniel H. ; Lemke, Raymond W.
Nature
Desjarlais, Michael P. ; Mattsson, Thomas M.
Hanshaw, Heath L. ; Lemke, Raymond W. ; Yu, Edmund Y. ; Desjarlais, Michael P. ; Mehlhorn, Thomas A.
Proceedings APS Shock Compression of Condensed Matter 2007
Desjarlais, Michael P. ; Mattsson, Thomas M.
Knudson, Marcus D. ; Desjarlais, Michael P. ; Lemke, Raymond W.
Desjarlais, Michael P. ; Knudson, Marcus D. ; Lemke, Raymond W.
Knudson, Marcus D. ; Lemke, Raymond W. ; Desjarlais, Michael P.
Cuneo, M.E. ; Lemke, Raymond W. ; Desjarlais, Michael P. ; Jennings, Christopher A. ; Sinars, Daniel S.
Proposed for publication in Physical Review Letters.
Desjarlais, Michael P. ; Mattsson, Thomas M.
Mehlhorn, Thomas A. ; Yu, Edmund Y. ; Vesey, Roger A. ; Cuneo, M.E. ; Jones, Brent M. ; Knudson, Marcus D. ; Sinars, Daniel S. ; Robinson, Allen C. ; Trucano, Timothy G. ; Brunner, Thomas A. ; Desjarlais, Michael P. ; Garasi, Christopher J. ; Haill, Thomas A. ; Hanshaw, Heath L. ; Lemke, Raymond W. ; Oliver, Bryan V. ; Peterson, Kyle J.
Desjarlais, Michael P.
Alexander, Charles S. ; Thompson, Aidan P. ; Chhabildas, Lalit C. ; Furnish, Michael D. ; Dolan, Daniel H. ; Davis, Jean-Paul D. ; Lemke, Raymond W. ; Desjarlais, Michael P. ; Hertel, Eugene S.
Modine, N.A. ; Wright, Alan F. ; Muller, Richard P. ; Sears, Mark P. ; Wills, Ann E. ; Desjarlais, Michael P.
A finite temperature version of 'exact-exchange' density functional theory (EXX) has been implemented in Sandia's Socorro code. The method uses the optimized effective potential (OEP) formalism and an efficient gradient-based iterative minimization of the energy. The derivation of the gradient is based on the density matrix, simplifying the extension to finite temperatures. A stand-alone all-electron exact-exchange capability has been developed for testing exact exchange and compatible correlation functionals on small systems. Calculations of eigenvalues for the helium atom, beryllium atom, and the hydrogen molecule are reported, showing excellent agreement with highly converged quantumMonte Carlo calculations. Several approaches to the generation of pseudopotentials for use in EXX calculations have been examined and are discussed. The difficult problem of finding a correlation functional compatible with EXX has been studied and some initial findings are reported.
Mattsson, Thomas M. ; Desjarlais, Michael P.
Lemke, Raymond W. ; Vesey, Roger A. ; Desjarlais, Michael P. ; Cuneo, M.E. ; Mehlhorn, Thomas A.
Cuneo, M.E. ; Leifeste, Gordon T. ; Smith, Ian C. ; Stygar, William A. ; Sinars, Daniel S. ; Bennett, Guy R. ; Yu, Edmund Y. ; Lemke, Raymond W. ; Desjarlais, Michael P. ; Adams, Richard G. ; Bliss, David E. ; Jones, Michael J.
Mattsson, Thomas M. ; Desjarlais, Michael P.
Desjarlais, Michael P.
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