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Your search keyword '"Cochrane, Kyle R."' showing total 27 results
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27 results on '"Cochrane, Kyle R."'

1. ALEGRA: Finite element modeling for shock hydrodynamics and multiphysics

Author

Niederhaus, John H.J., Bova, Steven W., Carleton, James B., Carpenter, John H., Cochrane, Kyle R., Crockatt, Michael M., Dong, Wen, Fuller, Timothy J., Granzow, Brian N., Ibanez, Daniel A., Kennon, Stephen R., Luchini, Christopher B., Moral, Ramón J., O’Brien, Christopher J., Powell, Michael J., Robinson, Allen C., Rodriguez, Angel E., Sanchez, Jason J., Scott, W. Alan, Siefert, Christopher M., Stagg, Alan K., Tezaur, Irina K., Voth, Thomas E., and Wilkes, John R.

Published
2023
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2. Review of the second charged-particle transport coefficient code comparison workshop

Author

Stanek, Lucas J., primary, Kononov, Alina, additional, Hansen, Stephanie B., additional, Haines, Brian M., additional, Hu, S. X., additional, Knapp, Patrick F., additional, Murillo, Michael S., additional, Stanton, Liam G., additional, Whitley, Heather D., additional, Baalrud, Scott D., additional, Babati, Lucas J., additional, Baczewski, Andrew D., additional, Bethkenhagen, Mandy, additional, Blanchet, Augustin, additional, Clay, Raymond C., additional, Cochrane, Kyle R., additional, Collins, Lee A., additional, Dumi, Amanda, additional, Faussurier, Gerald, additional, French, Martin, additional, Johnson, Zachary A., additional, Karasiev, Valentin V., additional, Kumar, Shashikant, additional, Lentz, Meghan K., additional, Melton, Cody A., additional, Nichols, Katarina A., additional, Petrov, George M., additional, Recoules, Vanina, additional, Redmer, Ronald, additional, Röpke, Gerd, additional, Schörner, Maximilian, additional, Shaffer, Nathaniel R., additional, Sharma, Vidushi, additional, Silvestri, Luciano G., additional, Soubiran, François, additional, Suryanarayana, Phanish, additional, Tacu, Mikael, additional, Townsend, Joshua P., additional, and White, Alexander J., additional

Published
2024
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3. Transport coefficients of warm dense matter from Kohn-Sham density functional theory.

Author

Melton, Cody A., Clay III, Raymond C., Cochrane, Kyle R., Dumi, Amanda, Gardiner, Thomas A., Lentz, Meghan K., and Townsend, Joshua P.

Subjects
DENSITY functional theory, KRAMERS-Kronig relations, MOLECULAR dynamics, THERMAL conductivity, OPTICAL properties, ELECTRIC stimulation
Abstract

We present a comprehensive study of transport coefficients including DC electrical conductivity and related optical properties, electrical contribution to the thermal conductivity, and the shear viscosity via ab initio molecular dynamics and density functional theory calculations on the "priority 1" cases from the "Second Charged-Particle Transport Coefficient Workshop" [Stanek et al., Phys. Plasmas (to be published 2024)]. The purpose of this work is to carefully document the entire workflow used to generate our reported transport coefficients, up to and including our definitions of finite size and statistical convergence, extrapolation techniques, and choice of thermodynamic ensembles. In pursuit of accurate optical properties, we also present a novel, simple, and highly accurate algorithm for evaluating the Kramers–Kronig relations. These heuristics are often not discussed in the literature, and it is hoped that this work will facilitate the reproducibility of our data. [ABSTRACT FROM AUTHOR]

Published
2024
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5. The equation of state and shock-driven decomposition of polymethylmethacrylate (PMMA).

Author

Coe, Joshua D., Lentz, Meghan, Velizhanin, Kirill A., Gammel, J. Tinka, Kaushagen, John, Jones, Keith, and Cochrane, Kyle R.

Subjects
POLYMETHYLMETHACRYLATE, MOLECULAR dynamics, EQUATIONS of state, CHEMICAL reactions, ACTIVATION energy
Abstract

We present new equations of state (EOS) for polymethylmethacrylate and its shock-driven decomposition products, generated in both tabular form and as linear U S − u p fits to all previously available shock data. Different approaches are taken for materials shocked above and below the apparent threshold for chemical reactions at pressures P ≈ 30 GPa. Both EOSs are calibrated to and compared with a broad array of experimental results, as well as new ab initio molecular dynamics simulations presented here. Comparisons are good in most cases, and we focus our particular attention on those observables that test the distinction between reactants and products. [ABSTRACT FROM AUTHOR]

Published
2022
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6. Simulation of asteroid deflection with a megajoule-class X-ray pulse

Author

Moore, Nathan W., Mesh, Mikhail, Sanchez, Jason J., Schaeuble, Marc-Andre, McCoy, Chad A., Aragon, Carlos R., Cochrane, Kyle R., Powell, Michael J., and Root, Seth

Abstract

The Chicxulub asteroid impact triggered mass extinction, mega-tsunamis and a spell of global warming that lasted for around 100,000 years. Although the recent Double Asteroid Redirection Test mission by NASA demonstrated that near-Earth objects can be successfully targeted, deflecting the most dangerous asteroids will require energy concentrations akin to nuclear explosions. However, targets suitable for practice missions are scarce. Here we demonstrate the simulation of asteroid deflection with an X-ray pulse from a dense argon plasma generated at the Z machine, a pulsed power device at Sandia National Laboratories. We use so-called X-ray scissors to place surrogate asteroidal material into free space, simultaneously severing supports and vapourizing the target surface. The ensuing explosion accelerates the mock asteroidal material in a scaled asteroid intercept mission. Deflection velocities of around 70 m s–1for silica targets agree with radiation-hydrodynamic model predictions. We scale these results to proposed interceptor energies and predict that asteroids up to a diameter of (4 ± 1) km can be deflected with this mechanism, showing a viable way to prepare for future planetary defence missions.

Published
2024
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8. Shock-ramp of SiO2 melt.

Author

Clark, Alisha N., Lane, J. Matthew D., Davis, Jean-Paul, Sarafian, Adam R., Cochrane, Kyle R., Townsend, Joshua P., and Jacobsen, Steven D.

Subjects
SPEED of sound, MATERIALS science, MELTWATER, MELTING, DYNAMIC simulation
Abstract

SiO2 glass has been shock-melted at 100 GPa and then ramp compressed on the Z Accelerator at Sandia National Laboratories. In a shock-ramp experiment, a shockless ramp wave follows the shock impact, isentropically compressing the sample. This technique provides access to off-Hugoniot states, which are of importance to both materials and planetary sciences. Here we present results from shock-ramp experiments for two compositions of SiO2 glass, one with 1000 ppm by weight and one with <1ppm OH. We observe an increased particle velocity at the window-interface for SiO2 melt with 1000 ppm OH relative to the anhydrous sample, suggesting higher sound speed for the hydrous silicate melt. We describe how the lower shock impedance of molten silicate relative to the LiF window precludes the usual approach of iterative Lagrangian analysis to extract compressibility from shock-ramp velocity measurements. To understand the observation of higher velocity for the hydrated sample, and to guide development of a new shock-ramp data analysis approach, we present results from LAMMPS molecular dynamic simulations for SiO2 with 0-1wt.% H2O. These simulations show that the incorporation of water into SiO2 melt decreases the compressibility at constant pressure, consistent with the experimental observation of a stiffer response for the hydrated SiO2 melt. [ABSTRACT FROM AUTHOR]

Published
2023
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9. DC electrical conductivity of platinum from ab initio simulations.

Author

Lentz, Meghan K., Townsend, Joshua P., and Cochrane, Kyle R.

Subjects
ELECTRIC conductivity, TRANSITION metals, BRILLOUIN zones, PLATINUM, ATOMIC number, GOVERNMENT laboratories
Abstract

Platinum is a highly unreactive transition metal whose properties make it desirable for experiments at Sandia National Laboratories' Z Pulsed Power Facility (Z). In order to improve the use of platinum as a material standard in shock compression experiments, we investigated the necessary procedure to produce high quality DC electrical conductivity calculations from den-sity functional theory using the Kubo Greenwood (KG) approximation. We studied the effects of changing several parameters involved in these calculations, all of which have some level of control over the calculated electrical conductivity. These parameters include the sampling of the Brillouin zone, smearing of the KG energy differences, the number of virtual orbitals included in the calculations, and the number of atomic configurations that are considered in the average electrical conductivity. [ABSTRACT FROM AUTHOR]

Published
2023
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11. Shock-ramp of SiO2 melt

Author

Clark, Alisha N., primary, Lane, J. Matthew D., additional, Davis, Jean-Paul, additional, Sarafian, Adam R., additional, Cochrane, Kyle R., additional, Townsend, Joshua P., additional, and Jacobsen, Steven D., additional

Published
2023
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14. Shock compression of niobium from first-principles.

Author

Weck, Philippe F., Townsend, Joshua P., Cochrane, Kyle R., Crockett, Scott D., and Moore, Nathan W.

Subjects
DIAMOND crystals, NIOBIUM, DENSITY functional theory, PHASE space, DIAMOND anvil cell, ECONOMIC shock, EQUATIONS of state, MOLECULAR dynamics
Abstract

The equation of state (EOS) of bulk niobium (Nb) was investigated within the framework of density functional theory, with Mermin's generalization to finite temperatures. The shock Hugoniot for fully-dense and porous Nb was obtained from canonical ab initio molecular dynamics simulations with Erpenbeck's approach based on the Rankine-Hugoniot jump conditions. The phase space was sampled along isotherms between 300 and 4000 K, for densities ranging from ρ = 5.5 to 12 g/cm 3. Results from simulations compare favorably with room-temperature multianvil and diamond anvil cell data for fully-dense Nb samples and with a recent tabulated SESAME EOS. The results of this study indicate that, for the application of weak and intermediate shocks, the tabular EOS models are expected to give reliable predictions. [ABSTRACT FROM AUTHOR]

Published
2019
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19. Liquid‐Vapor Coexistence and Critical Point of Mg 2 SiO 4 From Ab Initio Simulations.

Author

Townsend, Joshua P., Shohet, Gil, and Cochrane, Kyle R.

Subjects
CRITICAL point (Thermodynamics), EQUATIONS of state, ORIGIN of planets, VAPORIZATION, MOLECULAR dynamics, LAVES phases (Metallurgy), MAGNESIUM silicates
Abstract

Hypervelocity impact‐driven vaporization is characteristic of late‐stage planet formation. Yet the behavior and properties of liquid‐vapor mixtures of planetary materials of interest are typically unknown. Multiphase equations of state used in hydrodynamic simulations of planet impacts therefore lack reliable data for this important phenomenon. Here, we present the first constraints on the liquid‐vapor critical point and coexistence phase boundary of Mg2SiO4 computed from ab initio molecular dynamics simulations. We found that the vapor is depleted in magnesium and enriched in silica and oxygen, while the coexisting liquid is enriched in magnesium and depleted in oxygen, from which we infer vaporization is incongruent. The critical point was estimated from an equation of state fit to the data. The results are in line with recent calculations of MgSiO3 and together confirm that extant multiphase equation of state (EOS) models used in planetary accretion modeling significantly underestimate the amount of supercritical material postimpact. Key Points: Mg2SiO4 vaporizes incongruently and produces Mg‐poor vapor and O2 and SiO‐enriched vaporCritical point occurs at lower density and temperature than commonly used multiphase EOSGiant impact simulations underestimate amount of supercritical material postimpact [ABSTRACT FROM AUTHOR]

Published
2020
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26. Implosion dynamics and K-shell x-ray generation in large diameter stainless steel wire array Z pinches with various nesting configurations

Author

Jones, Brent, primary, Coverdale, Christine A., additional, Deeney, Christopher, additional, Sinars, Daniel B., additional, Waisman, Eduardo M., additional, Cuneo, Michael E., additional, Ampleford, David J., additional, LePell, P. David, additional, Cochrane, Kyle R., additional, Thornhill, J. Ward, additional, Apruzese, J. P., additional, Dasgupta, Arati, additional, Whitney, Kenneth G., additional, Clark, Robert W., additional, and Chittenden, Jeremy P., additional

Published
2008
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27. Liquid‐Vapor Coexistence and Critical Point of Mg2SiO4From Ab Initio Simulations

Author

Townsend, Joshua P., Shohet, Gil, and Cochrane, Kyle R.

Abstract

Hypervelocity impact‐driven vaporization is characteristic of late‐stage planet formation. Yet the behavior and properties of liquid‐vapor mixtures of planetary materials of interest are typically unknown. Multiphase equations of state used in hydrodynamic simulations of planet impacts therefore lack reliable data for this important phenomenon. Here, we present the first constraints on the liquid‐vapor critical point and coexistence phase boundary of Mg2SiO4computed from ab initio molecular dynamics simulations. We found that the vapor is depleted in magnesium and enriched in silica and oxygen, while the coexisting liquid is enriched in magnesium and depleted in oxygen, from which we infer vaporization is incongruent. The critical point was estimated from an equation of state fit to the data. The results are in line with recent calculations of MgSiO3and together confirm that extant multiphase equation of state (EOS) models used in planetary accretion modeling significantly underestimate the amount of supercritical material postimpact. Mg2SiO4vaporizes incongruently and produces Mg‐poor vapor and O2and SiO‐enriched vaporCritical point occurs at lower density and temperature than commonly used multiphase EOSGiant impact simulations underestimate amount of supercritical material postimpact

Published
2020
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