Professor Justin Wark: Publications

Shock induced α-ε Phase change in iron: Analysis of MD simulations and experiment

Aip Conference Proceedings 845 I (2006) 220-223

Authors:

J Hawreliak, K Rosolankova, JF Belak, G Collins, J Colvin, HM Davies, JH Eggert, TC Germann, B Holian, DH Kalantar, K Kadau, P Lomdahl, HE Lorenzana, J Sheppard, JS Stölken, JS Wark

Abstract:

Multimillion atom non-equilibrium molecular dynamics simulations for shock compressed iron are analyzed using Fourier methods to determine the long scale ordering of the crystal. By analyzing the location of the maxima in k-space we can determine the crystal structure and compression due to the shock. This report presents results from a 19.6GPa simulated shock in single crystal iron and compare them to recent experimental results of shock compressed iron where the crystal structure was determined using in-situ wide angle x-ray diffraction. © 2006 American Institute of Physics.

In situ diffraction measurements of lattice response due to shock loading, including direct observation of the alpha-epsilon phase transition in iron

INT J IMPACT ENG 33:1-12 (2006) 343-352

Authors:

DH Kalantar, GW Collins, JD Colvin, JH Eggert, J Hawreliak, HE Lorenzana, MA Meyers, RW Minich, K Rosolankova, MS Schneider, JS Stolken, JS Wark

Abstract:

In situ diffraction is a technique to probe directly the lattice response of materials during the shock loading process. It is used to record diffraction patterns from multiple lattice planes simultaneously. The application of this technique is described for laser-based shock experiments. The approach to analyze in situ wide-angle diffraction data is discussed. This is presented in the context of single crystal [001] iron shock experiments where uniaxial compression of the bee lattice by up to 6% was observed. Above the alpha-epsilon transition pressure, the lattice showed a collapse along the [001] direction by 15-18%. Additional diffraction lines appear that confirm the transformation of the iron crystal from the initial bee phase to the hcp phase. (C) 2006 Elsevier Ltd. All rights reserved.

Material dynamics under extreme conditions of pressure and strain rate

Materials Science and Technology SAGE Publications 22:4 (2006) 474-488

Authors:

BA Remington, P Allen, EM Bringa, J Hawreliak, D Ho, KT Lorenz, H Lorenzana, JM McNaney, MA Meyers, SW Pollaine, K Rosolankova, B Sadik, MS Schneider, D Swift, J Wark, B Yaakobi

Picosecond x-ray studies of coherent folded acoustic phonons in a periodic semiconductor heterostructure

Proceedings of SPIE--the International Society for Optical Engineering SPIE, the international society for optics and photonics 6118 (2006) 61180v-61180v-11

Authors:

Peter Sondhauss, Jörgen Larsson, Michael Harbst, Graham A Naylor, Anton Plech, Kees-Bertus Scheidt, Ola Synnergren, Michael Wulff, Justin S Wark

Analysis of the x-ray diffraction signal for the α- transition in shock-compressed iron: Simulation and experiment

Phys. Rev. B Condens. Matter Mater. Phys. 74:18 (2006)

Authors:

J Hawreliak, JD Colvin, JH Eggert, DH Kalantar, HE Lorenzana, J S. Stölken, HM Davies, TC Germann, BL Holian, K Kadau, PS Lomdahl, A Higginbotham, K Rosolankova, J Sheppard, JS Wark

Abstract:

Recent published work has shown that the phase change of shock-compressed iron along the [001] direction does transform to the [hexagonal close-packed (hcp)] phase similar to the case for static measurements. This article provides an in-depth analysis of the experiment and nonequilibrium molecular dynamics simulations, using x-ray diffraction in both cases to study the crystal structure upon transition. Both simulation and experiment are consistent with a compression and shuffle mechanism responsible for the phase change from body-centered cubic to hcp. Also both show a polycrystalline structure upon the phase transition, due to the four degenerate directions in which the phase change can occur. © 2006 The American Physical Society.

51��