Publications

Carpenter, John H.

A new copper equation of state is developed utilizing the available experimental data in addition to recent theoretical calculations. Semi-empirical models are fit to the data and the results are tabulated in the SNL SESAME format. Comparison to other copper EOS tables are given, along with recommendations of which tables provide the best accuracy.

Journal of Applied Physics

Cowen, Benjamin J.; Carpenter, John H.

The Corrected Rigid Spheres (CRIS) equation of state (EOS) model [Kerley, J. Chem. Phys. 73, 469 (1980); 73, 478 (1980); 73, 487 (1980)], developed from fluid perturbation theory using a hard sphere reference system, has been successfully used to calculate the EOS of many materials, including gases and metals. The radial distribution function (RDF) plays a pivotal role in choosing the sphere diameter, through a variational principle, as well as the thermodynamic response. Despite its success, the CRIS model has some shortcomings in that it predicts too large a temperature for liquid-vapor critical points, can break down at large compression, and is computationally expensive. We first demonstrate that an improved analytic representation of the hard sphere RDF does not alleviate these issues. Relaxing the strict adherence of the RDF to hard spheres allows an accurate fit to the isotherms and vapor dome of the Lennard-Jones fluid using an arbitrary reference system. The second order correction is eliminated, limiting the breakdown at large compression and significantly reducing the computation cost. The transferability of the new model to real systems is demonstrated on argon, with an improved vapor dome compared to the original CRIS model.

Garasi, Christopher J.; Olles, Joseph D.; Cochrane, Kyle C.; Carpenter, John H.; Ball, James P.; Modine, N.A.

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Cowen, Benjamin J.; Carpenter, John H.

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Carpenter, John H.; Robinson, Allen C.; Debusschere, Bert D.

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Physical Review B

Weck, Philippe F.; Cochrane, Kyle C.; Root, Seth R.; Lane, J.M.; Shulenburger, Luke N.; Carpenter, John H.; Sjostrom, Travis; Mattsson, Thomas M.; Vogler, Tracy V.

The shock Hugoniot for full-density and porous CeO2 was investigated in the liquid regime using ab initio molecular dynamics (AIMD) simulations with Erpenbeck's approach based on the Rankine-Hugoniot jump conditions. The phase space was sampled by carrying out NVT simulations for isotherms between 6000 and 100 000 K and densities ranging from ρ=2.5 to 20g/cm3. The impact of on-site Coulomb interaction corrections +U on the equation of state (EOS) obtained from AIMD simulations was assessed by direct comparison with results from standard density functional theory simulations. Classical molecular dynamics (CMD) simulations were also performed to model atomic-scale shock compression of larger porous CeO2 models. Results from AIMD and CMD compression simulations compare favorably with Z-machine shock data to 525 GPa and gas-gun data to 109 GPa for porous CeO2 samples. Using results from AIMD simulations, an accurate liquid-regime Mie-Grüneisen EOS was built for CeO2. In addition, a revised multiphase SESAME-Type EOS was constrained using AIMD results and experimental data generated in this work. This study demonstrates the necessity of acquiring data in the porous regime to increase the reliability of existing analytical EOS models.

Weck, Philippe F.; Cochrane, Kyle C.; Walker, Seth R.; Lane, James M.; Shulenburger, Luke S.; Carpenter, John H.; Mattsson, Thomas M.; Vogler, Tracy V.

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Carpenter, John H.

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Carpenter, John H.; Robinson, Allen C.; Debusschere, Bert D.

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Carpenter, John H.; Debusschere, Bert D.; Robinson, Allen C.

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Carpenter, John H.

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Carpenter, John H.

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Carpenter, John H.; Robinson, Allen C.; Debusschere, Bert D.; Wills, Ann E.

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Carpenter, John H.

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Brown, Justin L.; Seagle, Christopher T.; Carpenter, John H.

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Carpenter, John H.

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Journal of Applied Physics

Cochrane, Kyle C.; Lemke, Raymond W.; Riford, Z.; Carpenter, John H.

The electrical conductivity of materials under extremes of temperature and pressure is of crucial importance for a wide variety of phenomena, including planetary modeling, inertial confinement fusion, and pulsed power based dynamic materials experiments. There is a dearth of experimental techniques and data for highly compressed materials, even at known states such as along the principal isentrope and Hugoniot, where many pulsed power experiments occur. We present a method for developing, calibrating, and validating material conductivity models as used in magnetohydrodynamic (MHD) simulations. The difficulty in calibrating a conductivity model is in knowing where the model should be modified. Our method isolates those regions that will have an impact. It also quantitatively prioritizes which regions will have the most beneficial impact. Finally, it tracks the quantitative improvements to the conductivity model during each incremental adjustment. In this paper, we use an experiment on Sandia National Laboratories Z-machine to isentropically launch multiple flyer plates and, with the MHD code ALEGRA and the optimization code DAKOTA, calibrated the conductivity such that we matched an experimental figure of merit to +/-1%.

Mattsson, Thomas M.; Lemke, Raymond W.; Dolan, Daniel H.; Dalton, Devon D.; Brown, Justin L.; Tomlinson, Kurt T.; Robertson, Grafton K.; Knudson, Marcus D.; Harding, Eric H.; Mattsson, Ann E.; Carpenter, John H.; Drake, Richard R.; Cochrane, Kyle C.; Blue, Brent B.; Robinson, Allen C.

Abstract not provided.

Journal of Applied Physics

Lemke, Raymond W.; Dolan, Daniel H.; Dalton, D.G.; Brown, Justin L.; Tomlinson, K.; Robertson, G.R.; Knudson, Marcus D.; Harding, Eric H.; Mattsson, A.E.; Carpenter, John H.; Drake, Richard R.; Cochrane, Kyle C.; Blue, B.E.; Robinson, Allen C.; Mattsson, Thomas M.

We report on a new technique for obtaining off-Hugoniot pressure vs. density data for solid metals compressed to extreme pressure by a magnetically driven liner implosion on the Z-machine (Z) at Sandia National Laboratories. In our experiments, the liner comprises inner and outer metal tubes. The inner tube is composed of a sample material (e.g., Ta and Cu) whose compressed state is to be inferred. The outer tube is composed of Al and serves as the current carrying cathode. Another aluminum liner at much larger radius serves as the anode. A shaped current pulse quasi-isentropically compresses the sample as it implodes. The iterative method used to infer pressure vs. density requires two velocity measurements. Photonic Doppler velocimetry probes measure the implosion velocity of the free (inner) surface of the sample material and the explosion velocity of the anode free (outer) surface. These two velocities are used in conjunction with magnetohydrodynamic simulation and mathematical optimization to obtain the current driving the liner implosion, and to infer pressure and density in the sample through maximum compression. This new equation of state calibration technique is illustrated using a simulated experiment with a Cu sample. Monte Carlo uncertainty quantification of synthetic data establishes convergence criteria for experiments. Results are presented from experiments with Al/Ta, Al/Cu, and Al liners. Symmetric liner implosion with quasi-isentropic compression to peak pressure ∼1000 GPa is achieved in all cases. These experiments exhibit unexpectedly softer behavior above 200 GPa, which we conjecture is related to differences in the actual and modeled properties of aluminum.

Carpenter, John H.; Robinson, Allen C.; Debusschere, Bert D.; Wills, Ann E.

Abstract not provided.

Carpenter, John H.; Robinson, Allen C.; Debusschere, Bert D.; Wills, Ann E.

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Brown, Justin L.; Carpenter, John H.; Seagle, Christopher T.

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Robinson, Allen C.; Carpenter, John H.; Debusschere, Bert D.

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Robinson, Allen C.; Mattsson, Thomas M.; Shulenburger, Luke N.; Carpenter, John H.; Debusschere, Bert D.

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Magyar, Rudolph J.; Carpenter, John H.

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