Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session F20: Matter at Extreme Conditions: Static EOS and Materials ExperimentsFocus
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Sponsoring Units: GSCCM Chair: Sally June Tracy, Carnegie Inst of Washington Room: Room 212 |
Tuesday, March 7, 2023 8:00AM - 8:12AM |
F20.00001: Carbonic acid formation via a solid-solid reaction under high P-T conditions Minseob Kim, Young Jay Ryu, Choong-Shik Yoo We report the formation of anhydrate H2CO3 via a solid-solid reaction pathway under high P-T conditions using Raman spectroscopy, X-ray diffraction, and visual observations. The x-ray results showed that H2O was thermally diffused into a cubic (CO2-I) and a distorted cubic lattice (CO2-IV). At low P-T region, monohydrate H2CO3 (H2CO3·H2O) formed between CO2-I and ice-VII, whereas anhydrate H2CO3 was formed between CO2-IV and ice-VII at higher P-T region. The crystal structure of H2CO3 is orthorhombic and the calculated density lies between that of CO2-IV and ideal CO2(IV)/H2O(VII) mixture. Stability region of H2CO3 was determined between the lower bound of CO2-IV and the CO2-saturated ice melting line. The present results show that H2CO3 can be produced under higher P-T conditions in the Earth’s subduction zone, and suggesting an important role for H2CO2 in the water-rich planets |
Tuesday, March 7, 2023 8:12AM - 8:24AM |
F20.00002: Sound velocity and Equation of State of B4C Muhetaer Aihaiti, Charlie M Zoller, Rostislav Hrubiak, Curtis Keeney-Benson, Tyrel M McQueen, Lucas Pressley, Maddury Somayazulu, Russell J Hemley B4C, a light weight, impact-resistant, hard material, is used in a variety of applications that exploit these unique properties. However, the material fragments on high-velocity impacts, and laboratory studies provide evidence for pressure-induced amorphization. Si-doping in B4C has been shown to delay the amorphization to higher pressures. To understand this high-pressure performance of B4C, we performed ultrasonic and x-ray diffraction measurements under pressure using several techniques. Using a Paris-Edinburgh cell to investigate the structural and elastic properties of B4C to 7 GPa, we found that the longitudinal acoustic wave increases first with pressure, then flattened above 3 GPa. Complementary x-ray diffraction measurements provided a direct determination of the P-V-T equation of state of both B4C and Si-doped B4C to 3 GPa and 1200 K. |
Tuesday, March 7, 2023 8:24AM - 9:00AM |
F20.00003: Recent Advances in Static Compression Science at XFELs and Synchrotrons Invited Speaker: Malcolm I McMahon The diamond anvil cell (DAC) can exert multi-megabar pressures on samples by virtue of the very small volume of sample it compresses, which may be as small as 5microns in diameter and 1 micron thick on initial compression. In recent years, advances in x-ray focussing optics, and upgrades to the magnetic lattices of the 3rd generation synchrotrons such as the European Synchrotron Radiation Facility (ESRF), have resulted in the production of high-energy x-ray beams, focussed to sub-micron dimensions, which are ideally suited for probing such very small samples. Simultaneously, the start-up of the European XFEL (EuXFEL) has led to a long-awaited research programme using DACs on an XFEL, where the high-energy x-ray pulses can be used to both pump and probe samples contained within DACs. |
Tuesday, March 7, 2023 9:00AM - 9:12AM |
F20.00004: Neutron Scattering Study of the Quantum Magnet SrCu2(BO3)2 at High Pressure Mohamed Zayed, Ellen Fogh |
Tuesday, March 7, 2023 9:12AM - 9:24AM |
F20.00005: Pressure effect on hydrogen tunneling in alpha-Mn with the use of diamond anvils Alexander I Kolesnikov, Bianca Haberl, Andrey Podlesnyak, Matthew B Stone, Reinhard Boehler, Jaimie J Molaison Recently, we have studied the pressure effect on the tunneling mode and vibrational spectra of hydrogen in alpha-MnH0.07 by using inelastic neutron scattering (INS) [1]. Applying hydrostatic pressure up to 30 kbar was shown to shift both the hydrogen optical modes and the tunneling peak to higher energies. First-principles calculations reveal that the potential for hydrogen in alpha-Mn becomes overall steeper with increasing pressure. At the same time, the barrier height and its extent in the direction of tunneling decrease and the calculations predict significant changes of the dynamics of hydrogen in alpha-Mn at 100 kbar, when the estimated tunneling splitting of the hydrogen ground state exceeds the barrier height. In the present work, using our high-pressure polycrystalline diamond anvils cell for ~1 mm3 sample, recently developed at SNS [2], we confirmed the previous INS results at 30 kbar, and observed the disappearence of the tunneling peak at 70 kbar, in agreement with the prediction. |
Tuesday, March 7, 2023 9:24AM - 9:36AM |
F20.00006: Metallic hydrogen: the question of metastability William Ferreira, Morten Moeller, Kiran Linsuain, Jing Song, Ashal Salamat, Ranga P Dias, Isaac F Silvera We have studied the properties of MH under pressure in a diamond anvil cell. The reflectance was measured at five wavelengths in the near infrared, using narrow band light emitting diodes (LEDs) to establish that the sample was in the metallic phase at 480-500 GPa. MH has been predicted to possibly be metastable, i.e., it might remain in the metallic phase when the pressure is lifted. Theoretical predictions have scattered results, one predicting that the metastability pressure is ~ 200 GPa, and another that it is as low as 10-20 GPa. We have observed that MH is not metastable at zero pressure and possibly remains metallic until pressure was reduced below ~100 GPa. We shall discuss the techniques that were used for this determination. |
Tuesday, March 7, 2023 9:36AM - 9:48AM |
F20.00007: Accurate Equation of State of Fluid H2-He Mixtures. Charles M Zoller, Sakun Duwal, Vitali Prakapenka, Stella Chariton, Sergey N Tkachev, Muhtar Ahart, Russell J Hemley An accurate compositionally dependent ρ-P equation of state (EOS) for H2-He is necessary for constraining and validating internal structure and evolutionary models of gas giant planetary interiors. A high accuracy (within 1%) EOS for this system is also required for precompression experiments on these components. The EOS was determined from sound velocity measurements obtained with Brillouin scattering on 9:1 and 1:1 H2:He mixtures at 300 K with pressures up to 5.4 GPa. The ρ-P relations are accurate over the pressure range studied and indicate ideal mixing at both compositions within experimental error. Related physical quantities and methods for the calculation of the equation of state are discussed. |
Tuesday, March 7, 2023 9:48AM - 10:00AM |
F20.00008: Pressure-induced amorphization and enhanced magnetic order in EuSn2As2 Sudeshna Samanta, Wenli Bi, Yansun Yao, Weiwei Xie, Wei Xu, Jiyong Zhao, Esen E. Alp, Dongzhou Zhang, Jingui Xu, Yuming Xiao, Yogesh K Vohra In this work, we investigated the influence of pressure on a layered magnetic topological insulator EuSn2As2 by experimental probes including synchrotron X-ray diffraction (XRD), X-ray absorption (XAS), and Mössbauer spectroscopy (SMS) combined with theoretical calculations. EuSn2As2 undergoes a pressure-induced amorphization under the pressure of 30 GPa coinciding with a valence transition from Eu2+ toward Eu3+. High-pressure and low-temperature SMS in 151Eu has been adopted to study the magnetic state up to 33 GPa. The experimental data were further supported by theoretical analysis. Additionally, we reveal that the magnetic ordering temperature is largely enhanced reaching 110 K at 26 GPa from 25 K at ambient pressure. The mechanism of the pressure-induced amorphization and enhanced magnetic order as well as the correlation with valence transition will be discussed in detail. |
Tuesday, March 7, 2023 10:00AM - 10:12AM |
F20.00009: Unusual Compressive Behaviour in the Alkali Metals Christian V Storm, James D McHardy, Sarah E Finnegan, Edward J Pace, Michael G Stevenson, Simon G MacLeod, Matthew Duff, Malcolm I McMahon The alkali metals were long considered prototypical free-electron metals, with their simple bcc structure at ambient. However, high-pressure experiments have revealed several complex phases such as host-guest structures (Na-V, K-III, Rb-IV), large unit cells (Li-V, Rb-III), and electrides (Na-VI, K-VII, Rb-VII). While several phase transitions in the alkali metals are accompanied by volume discontinuities, we have recently identified significant anomalies in the compression curves of these elements, indicating that even within phases there may be changes in the electronic structure. We explore these anomalies with a particular focus on Rb, using linearisation plots based on the APL equation of state form which offer a poweful way to identify changes in the compressive behaviour. |
Tuesday, March 7, 2023 10:12AM - 10:24AM |
F20.00010: Accuracy and precision of a new microsecond-timescale temperature diagnostic for pulsed-heated diamond anvil cells Chris F Anto, Zachary M Geballe The melting temperature of iron and iron alloys at Earth's inner core boundary are crucial information for determining the temperature throughout Earth’s core [1]. The temperature is estimated to be upwards of 5400K [1], but there is little agreement on the actual value due to large uncertainties. As a first step towards more accurate melting curves of iron alloys at megabar pressures, we characterize the precision and accuracy of a newly-built temperature measurement apparatus at Carnegie Earth and Planets Lab. We send 100 to 800 microsecond pulses of energy through ambient-pressure samples of iridium, platinum, titanium, and tungsten, and collect thermal emissions as they melt, using our photomultiplier tube table setup. We find that accuracy is better than 41K, and precision is better than 20K at the known melting temperatures of iridium, platinum, and titanium. The tungsten sample melts at ~ 200 K lower temperature than the literature value, likely due to oxidation in air. These ambient-pressure tests pave the way for improved accuracy during high pressure melting experiments. |
Tuesday, March 7, 2023 10:24AM - 10:36AM |
F20.00011: Mapping Pressure Distribution in a Diamond Anvil Cell above 200 GPa Daniel J Campbell, Earl F O'Bannon, Jesse S Smith, Zsolt J Jenei At the highest pressures, diamond anvil cell experiments are unavoidably nonhydrostatic. The presence of deviatoric stress can, for example, shift the pressure at which structural transitions are found, or even whether they are present at all. Understanding how loading conditions change the degree of pressure inhomogeneity is crucial when comparing and evaluating different works. |
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