Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session M03: Materials in Extremes: Equation of State and Phase DiagramsFocus
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Sponsoring Units: GSCCM Chair: Patricia Kalita, Sandia National Laboratories Room: 107 |
Wednesday, March 4, 2020 11:15AM - 11:27AM |
M03.00001: Multiphase EOS Table for Gallium Carrie Prisbrey, Christine J Wu We developed the first LLNL multiphase equation of state (EOS) for Gallium (Ga) covering a wide range of density (10-7-103 g/cc) and temperature (1-109K). The EOS includes three known solid phases (I, II and III) and one Ga liquid. The EOS table accurately reproduces available experimental Hugoniot, isotherms and isobar data, as well as observed phase boundaries. We demonstrate that there is a significant uncertainty in predicted phase boundaries beyond the range of existing experimental observations, since they are highly sensitive to small changes in the free energy differences between the neighboring phases. EOS model uncertainty and variations will also be explored in this study. |
Wednesday, March 4, 2020 11:27AM - 11:39AM |
M03.00002: MgO at Multi-Megabar Pressures: Benchmarking the Equation of State and B1−B2 Transition Using Auxiliary-Field Quantum Monte Carlo Shuai Zhang, Fionn Malone, Miguel A Morales Studying materials at up to multi-megabar pressures is important for understanding the interiors of exoplanets and testing equation-of-state (EOS) models. However, it remains challenging to both experiments (e.g., B1–B2 transition pressure, Ptr, for MgO is uncertain by 130 GPa) and theory [two-parameter (zero-pressure bulk modulus K0 and its pressure derivative K′0) EOS is subject to >10% uncertainties for compression ratio >1.5, and prevalent density-functional-theory (DFT) computations can be biased by the exchange-correlation functional]. Advances in quantum Monte Carlo (QMC) have shown remarkable successes for solids. In this work, we develop and apply auxiliary-field (AF) QMC to benchmark the EOS and Ptr of MgO. In contrast to DFT predictions that vary by ~3% in equilibrium volume (V0), ~6% in K0 of B1 MgO, and ~30 GPa in Ptr, AFQMC can anchor all the three quantities with significantly reduced uncertainties, thereby providing an accurate and practical approach to benchmark materials properties at such extreme conditions. |
Wednesday, March 4, 2020 11:39AM - 11:51AM |
M03.00003: The body-centered cubic Fe phase under extreme conditions: Observed yet unnoticed. Anatoly Belonoshko The recently disclosed mechanism of the body-centered cubic Fe stabilization under extreme pressures and temperatures allows for a new interpretation of a number experimental observations. The high-PT bcc Fe is stabilized by a liquid-like self-diffusion. This means that Fe at high pressure and temperatures is in many respects similar to liquid. Such similarity is confusing to some experimentalists and makes them to interpret solid-solid hcp-bcc transition as melting. I will demonstrate that a number of experimental data sets get a better explanation in terms of the hcp-bcc transition rather than in terms of hcp-liquid transition. The new interpretation removes a number of controversies concerning the extreme part of Fe phase diagram. I will show that in a number of experiments the bcc Fe was observed yet remained unnoticed because of the unexpected properties of the emerging high-PT Fe bcc phase. |
Wednesday, March 4, 2020 11:51AM - 12:27PM |
M03.00004: Experimental observations on microstructure of iron and other metals at high pressures and temperatures Invited Speaker: Rostislav Hrubiak Materials subjected to high pressure (P) and high/low temperature (T) treatments in the diamond anvil cell (DAC) often exhibit complexity and inhomogeneity, on length scales ranging from nanometers to tens of microns. A recently developed ability to perform detailed spatially resolved characterizations of the inhomogeneity under high P, or in the high P-T treated samples, has allowed to unlock some of the complexity and to gain an understanding of several of emerging physical phenomena in high pressure sciences. |
Wednesday, March 4, 2020 12:27PM - 12:39PM |
M03.00005: Assessing the accuracy of first-principles DFT in describing van-der-Waals interactions in energetic molecular crystals at ambient and high pressure conditions Ivan Oleynik, Kien Nguyen-Cong Various density functional theory (DFT) functionals are evaluated in their ability to accurately describe vdW interactions in energetic molecular crystals, which are of critical importance to obtain an accurate isothermal equation of state as well as other basic thermodynamic properties of energetic materials. Equilibrium volumes of seven EM crystals are evaluated using several DFT functionals with or with- out semi-empirical Van der Waals corrections, as well as non-local van der Waals density functionals, and compared with available experimental data. By calculating vibrational spectra of energetic molecular crystals, zero point energy (ZPE) and thermal contributions at finite temperature to cold DFT data, pressure-dependent lattice parameters and equation of state are obtained at experimental temperatures, thus allowing direct quantitative comparison with experiment. Newly developed meta-GGA SCAN functional provides the best description of vdW interactions, and delivers an accurate EOS of EMs in a wide range of pressures and temperatures. |
Wednesday, March 4, 2020 12:39PM - 12:51PM |
M03.00006: Examination of the validity of quantum statistical potentials for carbon Heather Whitley, Michael Sean Murillo, Lorin Benedict, John I Castor, Frank R Graziani In recent years, high power laser facilities, such as NIF, and advanced diagnostics have enabled the determination of detailed properties of dense plasmas over unprecedented regimes. Understanding such plasmas, which may be partially degenerate and/or moderately coupled, represents a major challenge to the plasma physics community. One particular challenge for research in this area is the development of interaction potentials which appropriately incorporate the effects of high electron temperature. We examine the accuracy and applicability of approximate effective potentials in the study of structural and dynamic properties carbon in the partially and fully ionized regimes. The diffractive Coulomb potential is derived from an exact quantum solution for a pair of particles while the fermionic character of the electrons is handled via an effective Pauli potential. We compare computed pressures and internal energies for carbon to an equation of state model that was developed based on path integral Monte Carlo and density functional theory. Prepared by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-795399 |
Wednesday, March 4, 2020 12:51PM - 1:03PM |
M03.00007: Wide-ranged equation of state models for elements from the atom-in-jellium approach Lorin Benedict, Damian Swift, Thomas Lockard, Philip A Sterne, Mandy Bethkenhagen, Sebastien Hamel, Alfredo A. Correa, Raymond Smith, Christine J Wu
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Wednesday, March 4, 2020 1:03PM - 1:15PM |
M03.00008: A new multiphase wide range Equation of State for Nickel Travis Sjostrom, Giulia DeLorenzi-Venneri, Sven Peter Rudin A new equation of state for Nickel has been built and entered in the SESAME database. The EOS was built by Opensesame, based on the multiphase approach. Magnetic effects, derived from the experimental heat capacity, were included by an extra term in the electronic free energy. The solid phase was fitted to available experimental data for thermal expansion, heat capacity and bulk modulus and to data from new DFT calculations of the cold curve and phonon dispersions. The low temperature liquid was calculated, based on the V-T theory approach, from DFT data for the cold curve in the liquid. The high temperature liquid was fitted to new QMD calculations. |
Wednesday, March 4, 2020 1:15PM - 1:27PM |
M03.00009: Update on multi-megabar shockless compression at Sandia’s Z machine (2020) Jean-Paul Davis, Justin Brown Quasi-isentropic, shockless ramp-wave experiments promise accurate equation-of-state (EOS) data of materials in the solid phase at relatively low temperatures and multi-megabar (100’s GPa) pressures. In this range of pressure, isothermal diamond-anvil techniques have limited pressure accuracy due to reliance on theoretical EOS of calibration standards, thus accurate quasi-isentropic compression data would help immensely in constraining EOS models. Multi-megabar shockless compression experiments using the Z Machine at Sandia as a magnetic drive with stripline targets have been performed on many solid materials over the past decade. An update is given on recent results and developments, including experimental techniques, analysis methods, and uncertainty quantification. |
Wednesday, March 4, 2020 1:27PM - 1:39PM |
M03.00010: High-temperature, high-pressure behavior of lithium fluoride Kanani Lee, Sarah M. Arveson, Minta C Akin, Neil C Holmes, Bruce J Baer, Hyunchae Cynn Lithium fluoride (LiF) is used extensively as optical windows in dynamic compression experiments and is also used as pressure media and thermal insulation in diamond-anvil cell (DAC) experiments. In order to better understand this important high-pressure standard and ubiquitous window material, we present high-temperature isothermal equations of state of LiF below its melting curve as measured in a laser-heated DAC. These measurements complement already measured low-T isotherms [Myint et al., JCP, 2019] performed with resistively-heated DACs and will be used to generate phase-aware, thermally accurate equations of state for LiF. Above its previously determined melting curve [Boehler et al., PRL, 1997], LiF exhibits strong changes in absorption, similar to other alkali halides [Arveson et al., PRB, 2018]. We explore these changes in optical properties and the significant consequences they have for temperature measurements measured spectroscopically. |
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