Bulletin of the American Physical Society
22nd Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 67, Number 8
Monday–Friday, July 11–15, 2022; Anaheim, California
Session C04: EOS Fundamental Design, Modeling and Experiments IIFocus Recordings Available
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Chair: Scott Crockett, Los Alamos Natl Lab Room: Anaheim Marriott Platinum 2 |
Monday, July 11, 2022 11:00AM - 11:15AM |
C04.00001: Maximum Likelihood Estimation Approach: A strategy to automate EOS design. GREGORY ROBERT, vincent dubois, philippe LEGRAND, David Hebert Using the newly developed POOH code (program d'optimisation heuristique), we propose a systematic statistical approach to producing a multiphase equation of state (EOS). Each phase of the EOS is represented by its Helmholtz free energy which is the sum of the cold curve and the thermal contribution. For every contribution, the POOH code has a large set of models to choose from. Our goal is to automatise the process as far as possible, giving the most likely parameters of the EOS. To do this, the Maximum Likelihood Estimation (MLE) method is applied. The calibration database containing the expected values and their uncertainties is chosen to represent some interesting properties of the material. Here, we apply our procedure to aluminum, emphasizing the versatile aspect of the POOH code. Then, we compare our EOS to a large set of experiments that includes some alloys. |
Monday, July 11, 2022 11:15AM - 11:30AM |
C04.00002: Phase transitions and phase diagram of silicon carbide at exoplanetary core conditions Kien Nguyen-Cong, Anatoly B Belonoshko, Jonathan Willman, Sally J Tracy, Patricia Kalita, Tommy Ao, Raymond F Smith, Ivan Oleynik High pressure high temperature behavior of crystalline SiC is being actively investigated with the goal of delivering key data for developing interior models of carbon-rich exoplanets. Recent static and dynamic compression experiments uncovered substantial differences in transition pressure from ambient zinc blende (or hexagonal) to high pressure rocksalt phases. The melting curves of both ambient and high-pressure phases are also poorly constrained. To bridge this knowledge gap, quantum molecular dynamics (QMD) simulations of the SiC phase diagram and shock Hugoniots are performed within a broad range of pressures (up to 1 TPa) and temperatures (up to 50,000 K). The QMD results reconcile the puzzling difference between the static and dynamic shock compression experiments while delivering accurate equation of state of the solid and liquid phases as well as the SiC melting lines. The QMD simulations are in good agreement with recent dynamic compression experiments. |
Monday, July 11, 2022 11:30AM - 12:00PM |
C04.00003: Development of a multiphase equation of state for iron and its alloys Invited Speaker: Christine J Wu We present the construction of a new multiphase equation of state (EOS) for iron (Fe), consisting of the five phases: bcc, hcp, fcc, δ (high-T/low-P bcc), and liquid. The free energy models for the phases are constrained by fitting to experimental data in the lower pressure regime, and to the predictions of ab initio electronic structure calculations of various types at higher pressures and temperatures. We show that our resulting multiphase iron EOS is in excellent agreement with a broad swath of static and dynamic high-pressure experimental data. For Fe properties with conflicting data, such as diamond-anvil-cell melt curves, we have constructed EOS variations to match both lower-temperature and higher-temperature branches. We find that only one of these variations is consistent with the reported shock-melting pressure. This Fe EOS enables us to develop the EOSs of other Fe alloys using a recently implemented mixing algorithm. |
Monday, July 11, 2022 12:00PM - 12:15PM |
C04.00004: Validation of the compression regime of a new nickel Equation of State Kyle R Cochrane, Patricia Kalita, Chad A McCoy, Tommy Ao, Marcus Knudson, Travis Sjostrom Nickel is used for many applications, such as wire arrays on Sandia’s Z machine, and is also a constituent of alloys, such as stainless steel. A high-fidelity equation of state (EOS) is needed in order to design experiments using predictive simulations, which in turn require that the EOS is validated in the regime it is going to be used. We present experimental data taken from Sandia’s Z machine and the OMEGA EP laser facility, as well as density functional theory ab initio molecular dynamics simulations. These are used to guide the creation of a new, broad range EOS and validate it along the Hugoniot. |
Monday, July 11, 2022 12:15PM - 12:30PM |
C04.00005: Establishing Platinum as a shock compression standard to more than 2 TPa Patricia Kalita, Kyle R Cochrane, Justin L Brown, Chad A McCoy, Marcus Knudson, Sven P Rudin, Scott D Crockett Shock experiments to ever higher stress states allow to test numerical methods, physics theories, and uncover new unexpected behaviors of matter. However existing EOSs for standards are limited to about half a terapascal, and the problem with extrapolating to much higher pressures is that extrapolations come with significant uncertainties. We experimentally constrained the Pt standard up to > 2 TPa using shock compression on Sandia’s Z machine. We also carried out AIMD simulations and we designed a broad range EOS for Pt: SESAME 3732. Our work establishes Platinum as a shock compression standard to > 2 TPa. |
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