Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session D24: Matter at Extreme Conditions: Planetary Materials IIFocus Recordings Available
|
Hide Abstracts |
Sponsoring Units: GSCCM DCOMP Chair: Anatoly Belonoshko, Royal Institute of Technology Room: McCormick Place W-186C |
Monday, March 14, 2022 3:00PM - 3:36PM Withdrawn |
D24.00001: Synthesis of high-pressure phases of minerals Invited Speaker: Gabriel D Gwanmesia Accurate sound velocity and elasticity data for Earth minerals measured at high pressure and temperature are essential for interpreting the Earth's interior's seismic velocity and density profiles in terms of the Earth's mineralogy and composition. We have fabricated optimum acoustic-quality synthetic polycrystalline wadsleyite (β-Mg2SiO4) specimens containing controlled water (OH) contents using hot-pressing techniques developed in a multi-anvil Kawai-type high-pressure apparatus. We have measured the acoustic velocity and elasticity in the samples at simultaneous high pressure and temperature using interferometry techniques in a multi-anvil device installed at the 6-BM-B beamline of the Advanced Photon Light Source Argonne National Laboratory. Integrating the beamline software automated controls and the multi-anvil interferometry systems enables fast measurements (less than 1s) of the travel times of acoustic waves in the sample and the sample density and length from synchrotron X-ray diffraction and X-radiography measurements, respectively. We examine the effects on the elasticity due to water incorporation in the wadsleyite and the impact of the hydrous mineral data on the Earth's mineralogical and chemical composition. |
Monday, March 14, 2022 3:36PM - 3:48PM |
D24.00002: Phase Behaviors of Superionic Water at Planetary Conditions. Sebastien Hamel Most water in the universe may be superionic, and its thermodynamic and transport properties are crucial for planetary science but difficult to probe experimentally or theoretically. We use machine learning and free energy methods to overcome the limitations of quantum mechanical simulations, and characterize hydrogen diffusion, superionic transitions, and phase behaviors of water at extreme conditions. We predict that close-packed superionic phases, which have a fraction of mixed stacking for finite systems, are stable over a wide temperature and pressure range, while a body-centered cubic superionic phase is only thermodynamically stable in a small window but is kinetically favored. Our phase boundaries, which are consistent with the existing-albeit scarce-experimental observations, help resolve the fractions of insulating ice, different superionic phases, and liquid water inside of ice giants. |
Monday, March 14, 2022 3:48PM - 4:00PM |
D24.00003: Elusive plastic phase of Ice at the boundary of liquid water and Ice VII on dynamic compression of water Nilanjan Mitra Numerous investigations (both numerical and experimental) have demonstrated phase transformation of liquid water to that of ice VII “like” crystal structure upon dynamic compression. The diagnostics used in most of these experimental investigations include refractive index changes, electrical conductivity changes and/or dielectric changes from which the crystal lattice structure can be somewhat estimated. However, no detailed inter and intra molecular studies are done to characterize the observed phase of ice upon dynamic compression of liquid water. Translational and rotational diffusion characteristics of the resultant crystal structure are done to demonstrate the presence of the elusive plastic phase of ice typically hypothesized to be present at the boundary of the liquid water and ice VII. |
Monday, March 14, 2022 4:00PM - 4:12PM |
D24.00004: Spin state and thermochemical equilibrium in pppv Mg2SiO4 Tianqi Wan, Yang Sun, Renata M Wentzcovitch Under the extreme conditions of super-Earths’ interior, MgSiO3 post-perovskite (ppv), the last stable silicate phase in the earth’s mantle, is predicted to dissociate into Mg2SiO4 post-post-perovskite (pppv) and SiO2 (Wu et al., 2013; Umemoto et al., 2017). It should be the primary mantle silicate in super-Earths that recombines and dissociates into other silicates and oxides. Therefore, it is essential to understand the properties of this pppv silicate phase, especially in solid-solution with Fe2SiO4. Here we present an ab initio study on the electronic, structural, and vibrational properties of Fe-bearing pppv. We also construct a thermodynamic model to address thermochemical equilibrium among (Mg2-xFex)SiO4, (Mg1-xFex)SiO3, and (Mg1-xFex)O phases. These results will help model the mantle of super-Earth-type exoplanets. |
Monday, March 14, 2022 4:12PM - 4:24PM |
D24.00005: A systematic DFT study of mineral properties using ab initio workflows Qi Zhang, Renata M Wentzcovitch Materials computations, especially the ab initio ones, are intrinsically complex. These difficulties have inspired us to develop a workflow framework, express [1], to automate long and extensive sequences of the ab initio calculations. Various materials properties can be computed in express, e.g., phonon spectrum, static and thermal equations of state, static and high-temperature elasticity, and other thermodynamic properties. It helps users in the preparation of inputs, execution of simulations, and analysis of data. It also tracks the operations and steps that users performed and thus can restore interrupted or failed jobs. |
Monday, March 14, 2022 4:24PM - 4:36PM |
D24.00006: Ab initio lattice thermal conductivity of MgSiO3 across the perovskite-postperovskite phase transition Zhen Zhang, Renata M Wentzcovitch Lattice thermal conductivity (κ) of MgSiO3 postperovskite (MgPPv) under the Earth’s lower mantle (LM) high pressure-temperature conditions is studied using the phonon quasiparticle approach by combing ab initio molecular dynamics and lattice dynamics simulations. Phonon lifetimes are extracted from the phonon quasiparticle calculations, and the phonon group velocities are computed from the anharmonic phonon dispersions, which in principle capture full anharmonicity. κ is calculated by using the linearized Boltzmann transport equation. Systematic results of temperature and pressure dependences of κ of both MgPPv and MgSiO3 perovskite (MgPv) are demonstrated. MgPPv’s and MgPv’s κ are then modeled along the typical geotherm. It is found that throughout the lowermost mantle, including the D” region, κ of MgPPv is ~25% larger than that of MgPv, mainly due to MgPPv’s higher phonon velocities. Such a difference in phonon velocities between the two phases originates in the MgPPv’s relatively smaller primitive cell. Our calculations also suggest that the MgPv to MgPPv phase transition causes a ~20% enhancement in κ of the pyrolitic LM aggregate at the core-mantle boundary. |
Monday, March 14, 2022 4:36PM - 4:48PM |
D24.00007: Ultra-high-pressure behavior of Mg2SiO4 and Mg2GeO4: A combined x-ray diffraction and density functional approach. Rajkrishna Dutta, Sally J Tracy, Ronald E Cohen, Jing Yang, Dean Smith, Yue Meng, Stella Chariton, Vitali Prakapenka, Thomas S Duffy Changes in Silicon coordination in minerals influence their physical properties such as density, viscosity, and elemental affinities. However, there is no experimental evidence for silicon coordination greater than 6 in any high-pressure crystalline silicate. Higher coordinated phases can be important in large rocky exoplanets (mantle pressures up to ~1 TPa). |
Monday, March 14, 2022 4:48PM - 5:00PM |
D24.00008: Nature of the molecular-to-atomic transition in liquid silica at extreme conditions Shuai Zhang, Miguel A Morales, Raymond Jeanloz, Marius Millot, Suxing Hu Molecular-to-atomic transitions are often associated with changes in structural and transport properties and can have profound implications for different areas in high-energy-density (HED) and planetary sciences. SiO2 (silica) under extremely high pressures and temperatures is often encountered in HED experiments and is an important building block of planets. The molecular-to-atomic transition in liquid silica has been suggested by previous studies but the mechanism of the transition has not been fully understood, experimentally and theoretically. We have performed comprehensive first-principles calculations that combine analysis of the thermodynamic, structural, and electronic properties during the transition. Our calculated Hugoniots show good consistency with well-established experimental data. We have also found clear signatures of chemical bond dissociation during the transition and large sensitivity of the transition temperature to pressure. These results reconcile previous experiments1 and theories2 by providing direct evidence and clarification about the nature of this process important for HED and planetary sciences. |
Monday, March 14, 2022 5:00PM - 5:12PM |
D24.00009: Machine-learned interatomic potentials of dense hydrogen from diffusion Monte Carlo Scott Jensen, Yubo Yang, Hongwei Niu, Markus Holzmann, CARLO PIERLEONI, David M Ceperley Many aspects of the phase diagram of dense hydrogen remain poorly understood, sometimes even qualitatively. Dense hydrogen is predicted become a high-temperature superconductor at sufficiently high pressure and is crucial in determining the structure of gas giant planets. Addressing the entire phase diagram with accurate ab initio simulations like diffusion Monte Carlo (DMC) is not currently feasible due to the computational cost, which limits studies to small system sizes. Recently, machine-learned interatomic potentials trained on ab initio data have been applied in large-scale molecular dynamics simulations to approach the accuracy of the ab initio methods without the finite size errors. Typically, these have relied on density functional theory to generate the training data. Here we present the first large-scale publicly accessible DMC database for dense hydrogen, which allows training of machine-learned potentials with DMC accuracy. Using this database, we determine the melting curve of molecular hydrogen as a function of pressure in the range 50-200 GPa. While at lower pressure our result agrees with previous theory and experiment, we find a substantially higher melting temperature at higher pressures. |
Monday, March 14, 2022 5:12PM - 5:48PM |
D24.00010: Stability of CO2 and carbonate materials under extreme conditions Invited Speaker: Alberto Otero-de-la-Roza Carbon dioxide (CO2) in its free and anionic forms (carbonates and bicarbonates) is an essential component of the Earth's carbon cycle and a major contributor to climate change. A detailed knowledge of CO2 dynamics and stability under high pressure and temperature is essential to understand the Earth's carbon cycle as well as to design new strategies for separation and capture of CO2. Despite this, our current knowledge of the pressure-temperature phase diagram of many geologically relevant carbonates is fragmentary. In this talk, we present a combined computational and experimental study of the phase stability of CO2 and various carbonates of geological relevance: hunitite (Mg3Ca(CO3)4), ankerite (CaFe(CO3)2), alstonite (BaCa(CO3)2), gaspeite (Ni3Mg(CO3)4), and others. This work has been carried out using laser-heating and diamond-anvil cell synchrotron X-ray diffraction in order to recreate the pressure and temperature that dominate in the interior of the Earth. Density-functional theory calculations are used to predict the stability and structure of these phases under arbitrary conditions of temperature and pressure. Conclusions are drawn regarding the general behavior of carbonates and CO2 under extreme conditions and their potential geological relevance. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700