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 PP02: V: High-Pressure Virtual |
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Sponsoring Units: GSCCM Chair: Magdalena Waleska Aldana Segura, Universidad de San Carlos de Guatemala Room: Virtual Room 2 |
Tuesday, March 21, 2023 9:00AM - 9:12AM |
PP02.00001: AI-enhanced prediction of high-pressure phase transformations induced by electron-phonon interaction using random structure searching simulations Anguang Hu, Hsu Kiang (James) Ooi, Mohammad Sajjad Ghaemi Non-perturbation density functional theory calculations of electron-phonon interactions revealed the quantum degeneracy effect on phase transformations under high pressures. The degenerate energy levels generally occur around symmetry points and lines of its band structure in a solid, rendering reactive centers of phase transformations in momentum space. Immersive visualization of Lewis structures as a virtual reality approach enhances random structure searching simulations using machine learning for efficiently predicting high-pressure phase transformations. Such immersive visualization of Lewis structures furnishes a chemical bonding space to supervise random structure searching simulations using machine learning, providing both chemical and symmetry constraints to determine reactive centers of phase transformations. Further non-perturbation calculations of electron-phonon interactions can show details of the quantum degeneracy effects on high-pressure phase transformations. As an application, we performed predictive simulations of the high-pressure phase transformations of hydrazine borane induced by electron-phonon interaction. The high-pressure crystal structure of hydrazine borane obtained by simulation agrees well with experimental data. |
Tuesday, March 21, 2023 9:12AM - 9:24AM |
PP02.00002: Structure Search on H2-PRE Phase of Solid Hydrogen: Diffusion Monte Carlo Study Tom Ichibha, Yunwei Zhang, Kenta Hongo, Ryo Maezono, Fernando A Reboredo The structural phase diagram of solid hydrogen is important for condensed matter physics and planetary science. However, the different structures in the phase diagram are still debated due to the experimental difficulties at extreme conditions. Therefore, an accurate ab initio structure search is crucial to assist experiment. We used a combination of structural search algorithms, density functional theory and diffusion Monte Carlo methods to study the problem. We eventually found a new stable structure, P21/c-8, stable under high pressures of 400 – 600 GPa. Our predicted pressure range for P21/c-8's appearance correlates well with a phase found experimentally in hydrogen by infrared spectroscopy. In this talk, we will describe the context of our work from the simulation point of view. We will discuss our results in connection with the experimental evidence and other theoretical predictions.
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Tuesday, March 21, 2023 9:24AM - 9:36AM |
PP02.00003: Modeling of Interfacial Processes of Gas Hydrate Systems for Engineering Applications at Extreme Conditions Samuel Mathews, Andre Guerra, Alejandro Rey, Phillip Servio Gas hydrates are composed of a hydrogen bonded backbone of water molecules enclosing guest molecules in cages. While the equilibrium formation conditions lie in the megapascal range for gas hydrates, experimental conditions of formation and engineering environment involve extreme pressures in the gigapascal range. This project circumvents these issues by using molecular dynamics (MD) simulations to study gas hydrates. This work uses MD to characterize the temperature and pressure effects on the interfacial tension, energy of interfaces, and growth rate of natural gas hydrates understand their performance in extreme environments and prove that advanced computational characterization techniques explain structural and transport properties under extreme environments. Our work has shown that there is excellent agreement between sI methane hydrates and experimental values, with the interfacial energy decreasing with temperature. Preliminary results show that the sII natural gas hydrates show the same behavior. We have confirmed the presence of a novel pre-melting layer at the interface between the structures and produced temperature/pressure of surface tension. This information yields data to determine which conditions favor or hinder hydrate formation in applications of interest. |
Tuesday, March 21, 2023 9:36AM - 9:48AM Author not Attending |
PP02.00004: High pressure effects on plastic deformation of molecular crystals Zhaocheng Zhang The plastic deformation of energetic molecular crystals is of importance for reaction initiation and detonation. Void collapse and shear localization are mechanisms that lead to intense energy concentration and are thought to be responsible for initiation due to mechanical stimuli. Since these processes are generally induced by shock loading, it is essential to understand the effects of high pressure on plastic deformation in molecular crystals. In this work we consider molecular crystal HMX and evaluate by atomistic simulations the effect of pressure on the Peierls stress and mobility of dislocations, with implications for the pressure dependent yield stress and strain rate sensitivity. We also report the effect of pressure on the g-surface for the most active slip planes of HMX. Implications for the continuum-scale constitutive description of plasticity are discussed. |
Tuesday, March 21, 2023 9:48AM - 10:00AM |
PP02.00005: Structural Stability of Sr2IrO4 at High Pressure: A Density Functional Theory Investigation Boyang Zheng, Xiang Li, Vincent H Crespi Sr2IrO4 does not show a metallic state at high pressure (up to 185 GPa) [1] unlike what would be expected for a Mott insulator. Pressure-induced structural phase transitions, which occur at multiple pressures [1--3] in this material, may explain this lack of pressure-induced metallicity. Using density functional theory, we investigated the stability of different structures of Sr2IrO4 as a function of pressure through both the equation of state and the phonon frequencies as calculated by finite displacement. We also investigated the effect of uniaxial stress along the c axis, and show that a structural phase transition may occur at a much lower pressure than for hydrostatic conditions. |
Tuesday, March 21, 2023 10:00AM - 10:12AM |
PP02.00006: Monocrystalline sI Methane Hydrate's stability performance under pressure determined by the law of mixture Xiaodan Zhu, Alejandro Rey, Phillip Servio Gas hydrates, which can be found in the deep sea or permafrost zones, are a potential energy source. These severe circumstances, however, significantly impede exploration and laboratory study. This research aims to learn how methane hydrates behave under pressure by applying density functional theory to simulate extreme situations. According to the results of this research, each type of cage within the lattice serves a distinct purpose in the pressure stability limit. Up to the stability limit, the law of mixture can be utilized to predict mechanical properties. Based on phase occupancy, an equation was developed to compute the compressive stability limit. Furthermore, two fracture mechanisms beyond the stability limit have been identified. The methane hydrate stability results can be applied to other hydrates, hydrogen bonding systems, and guest-host structures. |
Tuesday, March 21, 2023 10:12AM - 10:24AM |
PP02.00007: Spin crossover in ferropericlase: beyond ideal HS-LS ideal solid solution model Jingyi Zhuang, Yang Sun, Renata M Wentzcovitch The pressure- and temperature-induced high spin (HS) to low spin (LS) crossover of Fe2+ ions in ferropericlase (Fp), Mg(1-x)FexO, affects mantle properties such as density, elasticity, thermal properties, iron partitioning between Fp and other co-existing phases, etc. It further affects how we interpret lower mantle observations. Here, we present results of thermodynamic properties computed using a free energy model that goes beyond the ideal HS-LS solid solution framework. As in the past, ab initio calculations were performed using the DFT+ USC method with structure and electronic configuration dependent USC. Results show the influence of iron-iron interactions (elastic or exchange type) on the pressure range of the crossover. Comparison with available experimental data shows considerably improved agreement over that of the ideal solid solution model. |
Tuesday, March 21, 2023 10:24AM - 10:36AM |
PP02.00008: Pressure induced structural transformation in Ni2Mn2-xInx shape memory alloys Brian Blankenau, Elif Ertekin, Ravhi Kumar, Tianyu Su The metamagnetic Heusler alloy Ni2Mn2-xInx (0.32<x<0.64) has garnered significant interest thanks to several technologically significant properties that result from a coupled magnetostructural phase transformation. These properties include the magnetocaloric and barrocaloric effects, shape memory effect, and large magnetoresistance. While the vast majority of studies have investigated the effects of alloy composition on the magnetostructural phase transformation in Ni2Mn2-xInx, analysis of the effects of pressure on the transformation are also relevant for practical utilization in real devices. We report the results of high energy synchrotron x-ray diffraction coupled with a diamond anvil cell to study the pressure induced magnetostructural transformation in Ni2Mn2-xInx. A composition of x=0.61 was chosen and both single crystal and powder samples were used. All measurements were carried out in collaboration with HPCAT at the Advanced Photon Source of Argonne National Laboratory. In the isothermal case, the sample pressure was increased incrementally from 2GPa up to 50GPa. A clear structural transformation from L21 austenite to a modulated phase was observed near 7GPa, with an additional transformation possible near 16GPa. We report on the structural phases that emerge under pressure, the transformation pathways, and the effects of hysteresis, and we present first-principles analysis of the role of magnetostructural coupling on the observed transformation behavior. |
Tuesday, March 21, 2023 10:36AM - 10:48AM |
PP02.00009: Ti-6Al-4V to over 1.2 Terapascals: Shock Hugoniot and off-Hugoniot Release Experiments, Ab-initio Calculations and a Broad-Range Multiphase EOS. Pat Kalita, Kyle R Cochrane, Marcus D Knudson, Seth Root, Tommy Ao, Carrie Blada, Jerry Jackson, Jeffry Gluth, Ed Scoglietti, Scott D Crockett The most used titanium alloy, Ti-6Al-4V (Ti64), has excellent mechanical and biocompatibility properties with applications in aerospace, defense, biomedical and more. We extend the principal shock Hugoniot for Ti64 to more than threefold compression, up to over 1.2 TPa with high-fidelity experimental shock compression data measured on Sandia's Z machine. A highly reliable multiphase Equation of State (EOS) for Ti64 is developed, spanning a broad range of temperature and pressures. Shock release data are also presented, which provide additional constraints on the EOS model, in an off-Hugoniot regime, where experimental data have not yet been reported. The high-precision experimental results and high-fidelity simulations demonstrate that the Hugoniot of the Ti64 alloy is stiffer than that of pure Ti and reveal that Ti64 melts on the Hugoniot at a significantly lower pressure and temperature than previously modelled. |
Tuesday, March 21, 2023 10:48AM - 11:00AM |
PP02.00010: The metal-semiconductor transition in compressed 2M-WSe2 QING DONG, Yuqiang Fang, Shujia Li, Yeonkyu Lee, Ran Liu, Bo Liu, Quanjun Li, Jaeyong Kim, Jeehoon Kim, Fuqiang Huang, Bingbing Liu The application of high pressure on layered transition metal dichalcogenides (TMDs) has always been an effective way to induce exotic physical properties and novel phenomena. Here, we performed a high-pressure investigation on a newly structured TMD: 2M-WSe2 up to ~80 GPa through electrical transport and synchrotron x-ray diffraction (XRD) measurements. Superconductivity emerges at ~3.1 GPa, reaching the maximum around 8.9 GPa, and then disappears upon further compression. With the disappearance of superconductivity, an unexpected metal-semiconductor transition (MST) occurs around 14.6 GPa. The XRD results demonstrate that the MST can be attributed to the pressure-induced interlayer structural modulation to the monoclinic P21/m phase. Hall effect measurement reveals that the MST is accompanied by a decrease in hole-type carrier density. In addition, the final stable P21/m phase exhibits excellent metallic properties, but superconductivity does not re-emerge. It is very rare finding this metal-semiconductor transition in TMDs. Our result reveals the critical role of interlayer modulation under pressure in shaping the physical properties of TMDs and further expands the research field for layered materials. |
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