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Molecular dynamics simulation of dynamic response of beryllium

AIP Conference Proceedings

Thompson, A.P.; Lane, James M.D.; 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.

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TYPE Journal Article YEAR 2012
OSTIScopus

Double shock experiments on the sandia z machine

AIP Conference Proceedings

Hanshaw, Heath L.; Knudson, Marcus D.; Martin, Matthew R.; 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.

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TYPE Conference YEAR 2012
OSTIScopus

Equation of state and transport property measurements of warm dense matter

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.

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TYPE SAND Report YEAR 2009
DOIOSTI
Results 101–125 of 177
Results 101–125 of 177