Physics and Chemistry of Matter Under Extreme Conditions

Conference: 2020: 70th ACA Annual Meeting
08/05/2020: 12:00 PM  - 3:00 PM 
Oral Session 


The application of extreme conditions such as pressure, temperature and field results in dramatic changes in all forms of matter. Under these conditions, matter undergoes phase transitions, displays rich new physical and chemical phenomena and can even yield new structures and materials not accessible in any other way. The aim of this session is thus to bring together the most recent advances and discoveries in both experimental and theoretical research that highlight these unique behaviors.

Therefore, the session will address the many behaviors that are observed under extreme conditions. It will cover structural, electronic and magnetic properties, phonon and lattice dynamics, new materials synthesis, plastic deformation and melting. In addition, this session will also provide a forum for highlighting the state-of-the-art synchrotron and neutron techniques that enable new experimental research opportunities. Finally, it will also provide a platform for developmental ideas to expand the scope of future materials research under extreme conditions.


Understanding High-Pressure Formation of Topologically Non-trivial Intermetallic Compounds via In-Situ X-ray Diffraction

12:00 PM - 12:15 PM 
The investigation of topologically non-trivial surface states is at the forefront of condensed matter physics and material science. Of particular interest is the concurrence of non-trivial topology with superconductivity which has sparked both fundamental questions about the intersection of these phenomena and revealed potential applications in quantum computing. Although the extensive exploration of temperature–composition phase spaces has enabled experimental realization of topologically non-trivial compounds, very few superconduct. This paucity of topologically non-trivial superconductors creates an impetus for alternate synthetic routes to discover new topologically non-trivial superconductors. A key criterion for accessing non-trivial topology is the combination of a large degree of spin–orbit coupling and mobile electrons in the correct symmetry. To realize new topologically non-trivial superconductor candidates, we chose to combine lead, the largest, non-radioactive, main-group element, as a source of spin-orbit coupling with transition metals as a source of mobile electrons. As lead reacts with late-transition metals to form superconducting intermetallic compounds and many transition-metal–lead binary compounds have suitable symmetry for non-trivial topology, we chose to target binary compounds that combine late-transition metals with lead as promising candidates for topologically non-trivial superconductivity. Among these binary systems, a few, such as, Ni–Pb, had no thermodynamically stable compounds reported despite thorough investigation of their binary temperature–composition phase space. By combining high-pressure, high-temperature synthesis with in-situ and ex-situ X-ray diffraction techniques, we synthesized and crystallographically characterized the first intermetallic compound in the Ni–Pb system, Ni[sub]3[/sub]Pb[sub]2[/sub]. The pseudo-hexagonal symmetry within the modulated Ni[sub]3[/sub]Pb[sub]2[/sub] structure and the Dirac cones predicted at the Fermi energy of the band structure suggest Ni[sub]3[/sub]Pb[sub]2[/sub] may exhibit non-trivial topology. Moreover, Ni[sub]3[/sub]Pb[sub]2[/sub] is recoverable to ambient conditions enabling further investigation of its electronic properties. Here, we present the high-pressure synthesis of Ni[sub]3[/sub]Pb[sub]2[/sub], our insight into its formation, and our progress investigating its properties. 

View Abstract 340


Alexandra Tamerius, Northwestern University Evanston, IL 

Computationally directed discovery of bismuth based binary intermetallic materials

12:15 PM - 12:30 PM 
Bismuth based intermetallic materials display an astounding array of exotic properties, from non-trivial topology in Na3Bi, to permanent magnetism in MnBi and superconductivity in NiBi and NiBi3. Underpinning much of this behavior is the ability of bismuth, as the heaviest nonradioactive element on the Periodic Table, to provide a source of large spin-orbit coupling when in contact with a spin bearing metal. However, due to the paucity of examples of bismuth binary intermetallic compounds, the metal-metal interactions that mediate coupling are not well understood. To gain insight into the origin of these exotic electronic and magnetic phenomena, it is necessary to discover new materials and correlate their electronic and magnetic properties with their structure. While the thermodynamic binary phases are well explored, extending our focus to mapping the phase space of metastable materials provides new opportunities to reveal compounds that challenge our understanding of emergent phenomena. To systematically explore the synthesis of metastable materials, we employed in situ diffraction techniques at high applied-pressures that serve as a tunable parameter for assessing new regions of phase space. Pressure alters the thermodynamic landscape without providing additional energy to facilitate phase changes and therefore, and may be manipulated to generate and then trap otherwise inaccessible materials. However, because the high-pressure phase space of even binary mixtures of metals is vast, we set out to direct our synthetic efforts with computational techniques. By employing high-throughput ab-initio random structure searching at different pressures, we identified promising candidate structures and the pressures at which they become stable. This directed our high-pressure in situ X-ray diffraction based experiments, resulting in the discovery of new molybdenum-bismuth intermetallic phases that form in the CuAl2 structure type. This material, MoBi2, not only represents the first known binary phases for mixtures of Mo-Bi. It also indicates the stability of this structure type for high-pressure bismuth containing intermetallic materials, providing a unique opportunity to compare how transition metal-bismuth bonds influence the electronic properties of these materials. 

View Abstract 343


Alison Altman, Northwestern University Evanston, IL 

Additional Author

Danna Freedman, Northwestern University Evanston, IL 

High Pressure Study on Novel Quantum Materials

12:30 PM - 1:00 PM 
Pressure provides a useful tool to precisely tune the interatomic distances in quantum materials, which is critical to understanding the organizing principles that govern electron dynamics with strong quantum fluctuations. Here, we report a comprehensive high-pressure study on the layered antiferromagnetic CaMn2Bi2 and discovered that it undergoes a pressure-induced structural phase transition with a large volume collapse ΔV/V ~ 10% at about 3 GPa. The crystal structure of the high-phase phase shows CaMn2Bi2 crystallizes in a new monoclinic structure with space group P21/m, and the puckered Mn-Mn honeycomb lattice in the ambient-pressure phase is found to be converted to one-dimensional (1D) zigzag ladder-like chains in the high-pressure phase. High-pressure resistivity measurements also evidenced the structural transformation as a sudden drop of resistivity by nearly two orders of magnitude at Pc = 2.4 GPa. In contrast to the semiconducting behavior at low temperatures of the low-pressure phase, the high-pressure monoclinic phase at P > Pc exhibits a metallic behavior down to the lowest temperature and displays in the resistivity curves two characteristic anomalies which show opposite pressure dependences. Considering the quasi-1D characteristics and enhanced electrical conductivity in the high-pressure phase, these anomalies might be associated with the formation of some spin/charge-density-wave states. The second electronic phase may result from the instability of the Fermi surface and strong electron-phonon coupling in the quasi-1D Mn-Mn chains. The theoretical assessments of electronic structures and total energies calculated for various magnetic structures of monoclinic CaMn2Bi2 indicate that the ferrimagnetic magnetic pattern is favored thermodynamically. 

View Abstract 360


Weiwei Xie

Coffee Break

1:00 PM - 1:30 PM 

High-Pressure Structural and Equation of State Study of Atacamite, a Copper Hydroxychloride Mineral

1:30 PM - 1:45 PM 
We studied the effect of pressure on atacamite, Cu2Cl(OH)3, to 8.79 GPa using single-crystal X-ray diffraction. Atacamite, crystallizes in orthorhombic space group Pnma with a = 6.0323(1) Å, b = 6.8672(2) Å, c = 9.1207(5) Å, V= 377.018(8) Å^3, and Z = 4. The (OH)3Cl group forms a tetrahedron, O3Cl, with two H(2) atoms positioned inside its O(2)...C1 edges, and one H(1) just outside its O(1)...Cl edge [1]. The Cu atoms reside in distorted octahedral (4+2)-coordination sites: Cu(1) is bonded to four hydroxyl groups and two Cl atoms while Cu(2) is bonded to five hydroxyl groups and one Cl atom. These Cu-octahedra are edge-linked as in the spinel structure [1]. The structure is stable throughout the pressure range studied but there is a distinct change in the equation of sate of atacamite at 3.5 GPa reflected in the change of the isothermal bulk modulus, K, as a function of pressure (Fig. 1). A 3rd-order Birch-Murnaghan equation of state fit to the P-V data up to 3.44 GPa yielded K=79.8(9) GPa with a very low dK/dP = 0.5(5). Above 3.5 GPa, a 3rd-order Birch-Murnaghan equation of state fit to the data yielded K=74.0(5) GPa and dK/dP = 3.6(1). The structural changes that occur at 3.5 GPa will be discussed in detail in the presentation. [1] Parise and Hyde (1986) Acta Cryst, C42: 1277-1280 

View Abstract 307


Nancy Ross, Geosciences, Virginia Tech Blacksburg, VA 

Additional Author

Jing Zhao, Virginia Tech Blacksburg, VA 

Observation of nine-fold coordinated amorphous TiO2 at high pressure

1:45 PM - 2:00 PM 
Understanding pressure-induced structural changes in amorphous dioxides (a-AO2) is of great importance in many fields of science. Here we report new experimental results of high pressure polyamorphism in amorphous TiO2 (a-TiO2) with the Ti-O coordination number (CN) close to 9. Our experimental data show that CN increases from 7.2 at 15.7 GPa, to 8.8 at 70.2 GPa, and finally reaches a plateau ~8.9 at pressures up to 85.7 GPa. We find that CN of both crystalline TiO2 and a-TiO2 follows a similar and systematic dependence on the ratio (γ) of the ionic radii of Ti and O. The γ of a-TiO2 is 0.614 at 15.7 GPa, which is similar to that of baddeleyite-type TiO2 (~0.61), and increases continuously with pressure. At 70.2 GPa, γ of a-TiO2 is 0.701, which is similar to that of cotunnite-type TiO2 (~0.693). It appears that the CN≈9 plateau of a-TiO2 correlates to the cotunnite-type and Fe2P-type polymorphs, which have the same CN=9 but correspond to different γ values. This CN-γ relationship is applicable to other a-AO2 of a-SiO2 and a-GeO2. All three compounds show surprisingly consistent between CN and γ, implying a unified relation between CN and γ in a-AO2. The established CN-γ relationship may be used to predict the compression behavior of a-AO2 compounds to extreme conditions. 

View Abstract 222


Yu Shu, High Pressure Collaborative Access Team, X-ray Division, Argonne Natl Lab Lemont, IL 

Additional Author(s)

Yoshio Kono, Geodynamics Research Center, Ehime University Ehime, Japan 
Guoyin Shen, High Pressure Collaborative Access Team, X-ray Division, Argonne Natl Lab Lemont, IL 

Compression rate dependence of the α to ω phase transition in titanium

2:00 PM - 2:15 PM 
Titanium (Ti) is commonly used in industrial applications such as aerospace, automotive and biomedical due to its corrosion resistance and high strength to density ratio. At high pressure(2.9-10.5 GPa), Ti transforms from the hexagonal close packed α phase to the open hexagonal ω phase.[1] The ω phase of Ti is brittle and recoverable at ambient pressure and therefore alters the properties of Ti. It is therefore important to understand this phase transformation of Ti as it is known to be affected by several factors including (i) the pressure medium used, (ii) the presence of impurities, and (iii) the compression rate.[1, 2] So far, Ti has mostly been compressed using 'slow' quasi-static or 'fast' shock compression; only one intermediate compression rate has so far been reported.[3, 4] In 2007, Evans et al. described a method for using a piezoelectric crystal to drive a diamond anvil cell, this is known as a dynamic diamond anvil cell (dDAC).[5] This method allows for controllable compression rates, ramp profiles and pressures. In the decade since, developments in both synchrotron technology (including fast detectors) and dDACs have made it possible to use time resolved X-ray diffraction to investigate phase transformations at significantly higher compression rates than conventional DACs, up to 102 TPa/s.[6, 7] These new developments have been used to further understand the phase transformation of Ti under hydrostatic and non-hydrostatic conditions at critical compression rates between static and shock compression rates. Recent dDAC experiments compressing Ti at compression rates between 2.5 and 3500 GPa/s indicate that at faster compression rates, under non-hydrostatic compression (without a pressure medium), the starting and completion pressure of the α to ω phase transformation in Ti increases. 1. Errandonea, D., et al., Pressure-induced transition in titanium metal: a systematic study of the effects of uniaxial stress. Physica B: Condensed Matter, 2005. 355(1-4): p. 116-125. 2. Velisavljevic, N., S. MacLeod, and H. Cynn, Titanium Alloys at Extreme Pressure Conditions, in Titanium Alloys - Towards Achieving Enhanced Properties for Diversified Applications. 2012, IntechOpen. 3. Greeff, C.W., D.R. Trinkle, and R.C. Albers, Shock-induced α–ω transition in titanium. Journal of Applied Physics, 2001. 90(5): p. 2221-2226. 4. Tomasino, D. and C.S. Yoo, Time-resolved X-ray diffraction of Ti in dynamic-DAC, in AIP Conference Proceedings. 2017. p. 060002. 5. Evans, W.J., et al., Dynamic diamond anvil cell (dDAC): a novel device for studying the dynamic-pressure properties of materials. Rev Sci Instrum, 2007. 78(7): p. 073904. 6. Jenei, Z., et al., New dynamic diamond anvil cells for tera-pascal per second fast compression x-ray diffraction experiments. Rev Sci Instrum, 2019. 90(6): p. 065114. 7. Sinogeikin, S.V., et al., Online remote control systems for static and dynamic compression and decompression using diamond anvil cells. Review of Scientific Instruments, 2015. 86(7): p. 072209. 

View Abstract 189


Larissa Huston, Los Alamos National Laboratory Los Alamos, NM 

Additional Author(s)

Eric K. Moss, Los Alamos National Laboratory Los Alamos, NM 
Jesse S. Smith, Argonne National Laboratory Argonne, IL 
Rachel Husband, DESY Hamburg, Germany 
Zsolt Jenei, Lawrence Livermore National Laboratory Livermore, CA 
Earl F. O'Bannon, Lawrence Livermore National Laboratory Livermore, CA 
Hanns-Peter Liermann, DESY Hamburg, Germany 
Blake T. Sturtevant, Los Alamos National Laboratory Los Alamos, NM 

The Crystallization Transformations Sequence as Ice is Compressed at Low Temperature: Avoidance of Amorphization

2:15 PM - 2:30 PM 
The compression of ice I is, as expected, seen to form high density amorphous (HDA) ice when compressed continuously to ~ 1 GPa. However, when ice I is compressed at a slower rate, with breaks between 1 Atm and 1 GPa, the formation of HDA can be avoided. Therefore resulting in the formation of a series of crystalline states. This demonstrates the crystalline-to-crystalline transformation sequence of the lowest energy structures when the amorphization of ice Ih into the HDA form is avoided. An explanation of the structural complexities of the crystalline transformation sequence indicate that high density amorphous ice is a result of an interrupted crystal-to-crystal transition between ice I and ice VIII, and is likely not a 'melting' process to a super-cooled liquid. Additionally, new data confirming the accurate calibration of our temperature measurement is provided, in addition to new thermal pathway analysis of the transformation sequence. 

View Abstract 351


Chris Tulk, Oak Ridge National Laboratory Oak Ridge, TN 

Additional Author(s)

Jamie Molaison, Oak Ridge National Laboratory Oak Ridge, TN 
Adam Makhluf, Department of Earth, Planetary and Space Sciences
Craig Manning, Department of Earth, Planetary and Space Sciences
Dennis Klug, National Research Council of Canada

Superconducting Superhydrides: Synthesis, Structure and Stability

2:30 PM - 3:00 PM 
Room-temperature superconductivity was first predicted in metallic hydrogen and then postulated in a number of hydrogen-rich materials at very high pressures /1,2/. The search for these superconductors led through hydrogen and related molecular hydrides culminating in the exciting discovery and concomitant theoretical simulations of superconductivity in H[sub]3[/sub]S /3-5/. The field practically exploded with this successful synergy between theory and experiment culminating in the discovery of superconductivity in YH[sub]x[/sub], LaH[sub]10-x[/sub] at temperatures as high as 265 K /6-10/. The pressures of synthesis make these compounds (as yet) unsuitable for neutron diffraction and therefore one relies on spectroscopy and x-ray diffraction to correlate with theoretical models and hypothesize the structures /8/. Our experiments reveal a very nebulous pathway to synthesis and stability and correlation between T[sub]c[/sub] and hydrogen stoichiometry. This talk will focus on the structure and stability aspects of these interesting class of compounds that need to be well understood to have a reproducible pathway to synthesis and validation of other properties including Meissner effect. [b]Acknowledgements[/b]: The synchrotron x-ray diffraction measurements were carried out at 16-ID-B of HPCAT at the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. Funding is acknowledged from DOE-BES, DOE-NNSA and NSF-DMR. [b]References[/b]: /1/ N. W. Ashcroft, [i]Metallic Hydrogen: A High-Temperature Superconductor?[/i], Phys. Rev. Lett., [b]21[/b], 1748 (1968). /2/ N. W. Ashcroft, [i]Hydrogen Dominant Metallic Alloys: High Temperature Superconductors?[/i], Phys. Rev. Lett., [b]92[/b], 187002 (2004). /3/ A. P. Drozdov et. al, [i]Conventional Superconductivity at 203 Kelvin at High Pressures in the Sulfur Hydride System[/i], [b]525[/b], 73 (2015). /4/ Li, Y. et. al, [i]The metallization and superconductivity of dense hydrogen sulfide.[/i], J. Chem. Phys. [b]140[/b], 174712 (2014). /5/ Duan, D. et al. [i]Pressure-induced metallization of dense (H[sub]2[/sub]S)[sub]2[/sub]H[sub]2[/sub] with high-T[sub]c[/sub] superconductivity[/i]. Sci. Rep. [b]4[/b], 6968 (2014). /6/ Hanyu Liu et. al, [i]Potential high-Tc superconducting lanthanum and yttrium hydrides at high pressure[/i], PNAS, [b]114[/b], 6990 (2017). /7/ P.P. Kong et. al, [i]Superconductivity up to 243 K in yttrium hydrides under high pressure[/i], arXiv:1909.10482 (2019). /8/ Somayazulu, M. et al. [i]Evidence for superconductivity above 260 K in lanthanum superhydride at megabar pressures[/i]. Phys. Rev. Lett. [b]122[/b], 027001 (2019). /9/ Drozdov, A. P. et al. [i]Superconductivity at 250 K in lanthanum hydride under high pressures[/i]. Nature [b]569[/b], 528–531 (2019). 

View Abstract 365


Maddury Somayazulu