Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session J40: Matter in Extreme Environments II: Liquids, Geological, and Complex MaterialsFocus
|
Hide Abstracts |
Sponsoring Units: DCOMP DMP Chair: Tiange Bi Room: 705 |
Tuesday, March 3, 2020 2:30PM - 3:06PM |
J40.00001: Using liquid informed searches to predict high pressure and finite temperature phase transitions Invited Speaker: Stanimir Bonev
|
Tuesday, March 3, 2020 3:06PM - 3:18PM |
J40.00002: Ab initio investigation of post-PPV transitions in MgGeO3 and NaMgF3 Koichiro Umemoto, Renata Wentzcovitch We present an ab initio investigation of the pressure induced behavior of MgGeO3 and NaMgF3, traditional low-pressure analogs (LPAs) of MgSiO3. The latter undergoes post-post-perovskite (post-PPV) transitions which are exceedingly important in planetary sciences, but at very high pressures of >~500 GPa [1-3]. Although neither MgGeO3 nor NaMgF3 are perfect LPAs of MgSiO3, in overall both display similar dissociation and recombination transitions and the novel types of phases displayed by MgSiO3 but at much lower pressures easily achievable in diamond anvil cells. Both systems also confirm the ultimate tendency of MgSiO3 toward the dissociation into its elementary binaries, i.e., AX and BX2. We also predict potential metastable phase transitions that may occur more easily than dissociation/recombination reactions under insufficiently heated compression. |
Tuesday, March 3, 2020 3:18PM - 3:30PM |
J40.00003: First-principles DFT molecular dynamics simulations of Fe, H, and FeH fluids in planetary interiors Ronald Cohen Using density functional theory and the QUANTUM ESPRESSO code, first-principles molecular dynamics simulations have been performed over a wide range of pressures and temperatures, for pure Fe, pure H, and Fe-H solutions. Pressures range from 0 to 100 MB (10 TPa) and temperatures from 2000-40000 K. From these results the equations of state are fit for extreme conditions in planetary core from Earth to Jupiter and beyond. Transport properties are also being computed from snapshots of the MD runs. Good agreement is found with new experiments and results are consistent with a thermally driven dynamo over Earth history. |
Tuesday, March 3, 2020 3:30PM - 3:42PM |
J40.00004: The post-perovskite transition in Fe- and Al-bearing bridgmanite: effects on seismic observables Renata Wentzcovitch, Juan J Valencia-Cardona, gaurav shukla, Kanchan Sarkar The major mineral phase of the Earth’s lower mantle, (Al,Fe)-bearing bridgmanite, transitions to a seemingly layered structure known as post-perovskite at Earth’s deep lower mantle conditions. Despite extensive investigations, there are still important aspects of this transformation that need clarification. Here, we address this transition in (Al3+, Fe3+)-, (Al3+)-, (Fe2+)- and (Fe3+)-bearing bridgmanite using ab initio calculations, particularly the phase boundary dependence on the chemistry and acoustic velocity changes across this transformation. These results help us to constrain possible seismic signatures of this phase transition, which is necessary for a better understanding of the nature of the D” region. While our results are consistent with previous mineral physics studies, we find that the seismic features produced by the post-perovskite transition depend on the chemical composition of bridgmanite. Therefore, the absence of a D“ seismic discontinuity or signature of a double-crossing of the post-perovskite phase boundary has clear implications for the local aggregate chemistry and/or temperature. |
Tuesday, March 3, 2020 3:42PM - 3:54PM |
J40.00005: Life in Extreme Environments: Material Properties of the Enzymes Toshiko Ichiye Life on Earth has been found in many extremes of pressure P and temperature T. Understanding how life works at high P and high T has implications for the origin of life on Earth and for the search for extraterrestrial life. In addition, extremes of P and T are used in sterilization and food preservation. To understand how the proteins necessary for life can function at extremes, we use a combination of molecular dynamics simulations of enzymes in aqueous solution, combined with experimental data, to understand how their material properties affect their biochemical activity. We will discuss the effects of P and T on enzymes, evolutionary timescale adaptations in the material properties of enzymes for extremes, and rapid response changes in the intracellular environment to protect enzymes against extremes. |
Tuesday, March 3, 2020 3:54PM - 4:06PM |
J40.00006: Express: nonstop calculations with the Quantum ESPRESSO Qi Zhang, Michel Marcondes, Hongjin Wang, Jingyi Zhuang, Pedro da Silveira, Renata Wentzcovitch The intrinsic complexity of ab initio mineral physics studies inspired the development of workflows to automate long and extensive sequences of ab initio calculations [1]. This complexity emerges from the need to sample thermodynamic and chemical phase space for useful geophysical applications. Here we introduce Express, a new generation of Python and Julia workflows designed to facilitate calculations of thermoelastic and thermochemical properties of materials. |
Tuesday, March 3, 2020 4:06PM - 4:18PM |
J40.00007: Ab initio simulation of heat and charge transport in water at planetary pT conditions Federico Grasselli, Lars Peter Stixrude, Stefano Baroni The transport properties of water at extreme pT conditions govern the evolution of icy planets, such as Uranus and Neptune, and moons, such as Europa or Encelado. New theoretical and data-analysis methods have been recently developed to estimate accurate transport coefficients of electronically gapped materials from ab initio equilibrium molecular dynamics and the Green-Kubo theory of linear response [1-3]. In this talk we report on recent results of the application of these methods to heat and charge transport in water at the extreme pT conditions occurring in the interior of icy giants, in all the different relevant phases (partially dissociated liquid, solid, and super-ionic) [4]. These results are finally employed to build a model of the thermal evolution of Uranus, which accounts for its hitherto poorly understood very low luminosity. |
Tuesday, March 3, 2020 4:18PM - 4:30PM |
J40.00008: First-principles predictions of electrical and thermal conductivity of liquid and solid iron at Earth core conditions Kai Luo, Ronald Cohen Transport properties such as thermal and electrical conductivities of the liquid iron alloy are critical in understanding the dynamic history of Earth's outer core and the evolution of the geomagnetic field. |
Tuesday, March 3, 2020 4:30PM - 4:42PM |
J40.00009: Anomalous structural behaviour near a Mott transition in compressed Ca2RuO4 Harry Keen, Stephen R Julian, Andreas Hermann Ca2RuO4 has a rich phase diagram, featuring a metal-insulator transition with a structural distortion upon cooling, antiferromagnetic ordering upon further cooling, and metallisation and ferromagnetic order, followed by a further structural transition, under pressure. It is one end member of the Ca(2-x)Sr(x)RuO4 series that includes the proposed triplet superconductor Sr2RuO4 at the other end. Ca2RuO4 shows intriguing collective phenomena in its own right, several of which are intricately linked to structural distortions of the RuO6 octahedra, which in turn are susceptible to pressure-induced changes. In fact, Ca2RuO4 shows an unusual c-lattice expansion under hydrostatic compression. However, the structural and electronic properties of Ca2RuO4 under pressure have not been investigated in detail before. Here, we study the high-pressure phase evolution of Ca2RuO4 using density functional theory (DFT) and DFT+U calculations. We show that the c-lattice expansion in the metallic high-pressure phase as well as details of the octahedral arrangements can be described if the on-site repulsion U is fine-tuned appropriately. The sensitivity to the size of U highlights how close the metallic phase remains to the Mott insulating phase. |
Tuesday, March 3, 2020 4:42PM - 4:54PM |
J40.00010: Theoretical Prediction of Novel Materials with the XtalOpt Evolutionary Algorithm Xiaoyu Wang, Patrick Avery, Davide M. Proserpio, Cormac Toher, Stefano Curtarolo, Eva Zurek The XtalOpt evolutionary algorithm for crystal structure prediction has been extended to enable the prediction of materials with specific properties. A fitness function has been implemented wherein the user can denote the percent contribution that enthalpy and the property (e.g. Vickers hardness obtained via a macroscopic hardness model and the shear modulus as determined via machine learning, percentage of hydrogen atoms that do not form H-H bonds, or density of states at the Fermi level) have on the fitness function. We have used XtalOpt to search for hard and stable carbon allotropes. Several novel carbon allotropes that are superconducting or posess super-long sp3-sp3 bonds were found. We also discovered novel hydrides that could potentially be conventional superconductors. |
Tuesday, March 3, 2020 4:54PM - 5:06PM |
J40.00011: Ab initio investigation of hydrogen-bond disorder in δ-AlOOH Chenxing Luo, Tianqi Wan, Ziyu Cai, Koichiro Umemoto, Renata Wentzcovitch δ-AlOOH (δ) is an important carrier of water in the lower mantle. Attempts to resolve the structure of δ revealed that hydrogen bonds (H-bond) “symmetrize” under compression in a process similar to the high-pressure ice VII- or ice VIII-X transition. Like H2O-ice, δ has its own “ice-disorder rules” and disorder is also observed experimentally prior to H-bond symmetrization [1]. H-bond disorder in δ had been suggested by an ab initio study as a possibility based on its broad band of Raman active OH-stretching modes [2]. |
Tuesday, March 3, 2020 5:06PM - 5:18PM |
J40.00012: Thermal Conductivity of CaSiO3 Perovskite at Lower Mantle Conditions Zhen Zhang, Kotaro Onga, Dong-Bo Zhang, Kenji Ohta, Tao Sun, Kei Hirose, Renata Wentzcovitch Thermal conductivity (κ) of mantle minerals modulates strongly both the style of mantle convection and the time scale of the mantle and core cooling. It is therefore a fundamental parameter for geodynamic modeling. Cubic CaSiO3 perovskite (CaPv) is believed to be the third most abundant mineral in the lower mantle (LM) (6 – 10 wt%). However, despite its importance, investigations of its properties are challenging because of its strong anharmonicity, particularly κ since prevailing theoretical approaches encounter difficulties in dealing with its strong anharmonicity. Experimental measurements at relevant high pressures and temperatures are equally challenging. Therefore, no previous estimate of CaPv’s κ exists at mantle conditions, experimental or theoretical. Here we present ab initio quantum mechanical results of this property obtained using an established phonon quasiparticle approach that can address the strongly anharmonic situation in CaPv. These results are substantiated by direct experimental measurements of this property at LM conditions. These results and data agree very well and reveal a surprisingly large κ of cubic CaPv compared to MgSiO3-perovskite, which is only weakly anharmonic. |
Tuesday, March 3, 2020 5:18PM - 5:30PM |
J40.00013: Determination of Diffusion Constants and Partial Pressures in the Adsorption of Methane-Propane and Methane-Ethane Mixtures Valleroy Zachary, Gonzalo Dos Santos, Todd Lombardi, Carlos Wexler Natural gas (NG) has advantages vs. gasoline/diesel: lower CO2 emissions per unit energy, less emission of NOx’s, particulate matter and unburned hydrocarbons. However, storing NG is problematic due to its low density, requiring very high pressures, costly compression and storage systems. A solution is storage by adsorption in porous media such as activated carbon (AC). NG is comprised mainly of methane, thus most studies have focused on adsorption of pure methane. Here we investigate the influence of heavier alkanes commonly found in NG (propane, ethane) on the adsorption process. |
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