A5079911171- High-pressure geophysics and materials
- Geological and Geochemical Analysis
- Rare-earth and actinide compounds
- Glass properties and applications
- Crystal Structures and Properties
- Diamond and Carbon-based Materials Research
- Iron-based superconductors research
- Magnetic Properties of Alloys
- Electronic and Structural Properties of Oxides
- Advanced Chemical Physics Studies
- Boron and Carbon Nanomaterials Research
- Magnetic and transport properties of perovskites and related materials
- Quantum Dots Synthesis And Properties
- Quantum, superfluid, helium dynamics
- earthquake and tectonic studies
- Advanced Condensed Matter Physics
- X-ray Diffraction in Crystallography
- Atomic and Subatomic Physics Research
- Geomagnetism and Paleomagnetism Studies
- Chalcogenide Semiconductor Thin Films
- Phase Equilibria and Thermodynamics
- Iron oxide chemistry and applications
- Energetic Materials and Combustion
- Intermetallics and Advanced Alloy Properties
- Nuclear Physics and Applications
Argonne National Laboratory
2006-2024
Carnegie Institution for Science
2006-2018
Geophysical Laboratory
2006-2018
Carnegie Observatories
2006-2007
National Synchrotron Radiation Research Center
2005-2006
University of Chicago
2006
Silicate melts at the top of transition zone and core-mantle boundary have significant influences on dynamics properties Earth's interior. MgSiO3-rich silicate were among primary components magma ocean thus played essential roles in chemical differentiation early Earth. Diverse macroscopic interior, such as density, viscosity, crystal-melt partitioning, depend their electronic short-range local structures high pressures temperatures. Despite many geophysical geodynamic problems, little is...
Knowledge of the electronic structure amorphous and liquid silica at high pressures is essential to understanding their complex properties ranging from melt in magma glass optics, electronics, material science. Here we present oxygen near $K$-edge spectra ${\mathrm{SiO}}_{2}$ $51\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ obtained using x-ray Raman scattering a diamond-anvil cell. The below $\ensuremath{\sim}10\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ are consistent with those quartz coesite,...
The near K-edge structure of oxygen in liquid water and ices III, II, IX at 0.25 GPa several low temperatures down to 4 K has been studied using inelastic x-ray scattering 9884.7 eV with a total energy resolution 305 175 meV. A marked decrease the preedge intensity from phase ice III II is attributed ordering hydrogen bonds proton-ordered lattice latter phases. Density functional theory calculations including influence Madelung potential crystal correctly account for remaining feature....
A drastically altered chemistry was recently discovered in the Fe-O-H system under deep Earth conditions, involving formation of iron superoxide (FeO2Hx with x = 0 to 1), but puzzling crystal this at high pressures is largely unknown. Here we present evidence that despite O/Fe ratio FeO2Hx, remains ferrous, spin-paired and non-magnetic state 60-133 GPa, while presence hydrogen has minimal effects on valence iron. The reduced accompanied by oxidized oxygen due oxygen-oxygen interactions. not...
Understanding structural stability and phase transformation of nanoparticles under high pressure is great scientific interest, as it one the crucial factors for design, synthesis, application materials. Even though high-pressure research on nanomaterials has been widely conducted, their shape-dependent transition behavior still remains unclear. Examples transitions CdS are very limited, despite fact that most studied wide band gap semiconductors. Here we have employed in situ synchrotron...
When subjected to high pressure and extensive x-radiation, water (H2O) molecules cleaved, forming O-O H-H bonds. The oxygen (O) hydrogen (H) framework in ice VII was converted into a molecular alloy of O2 H2. X-ray diffraction, x-ray Raman scattering, optical spectroscopy demonstrated that this crystalline solid differs from previously known phases. It remained stable with respect variations pressure, temperature, further laser exposure, thus opening new possibilities for studying...
Significance When compressed above megabar pressures (100 GPa), glasses may undergo structural transitions into more densely packed networks that differ from those at ambient pressure. While inelastic X-ray scattering (IXS) provides a rare opportunity to probe the pressure-induced bonding transitions, decade of efforts collect an IXS signal any matters beyond 100 GPa have not been successful. Here, spectra for B 2 O 3 up ∼120 revealed its unique densification paths characterized with...
Abstract High-Pressure Collaborative Access Team (HPCAT) is a synchrotron-based facility located at the Advanced Photon Source (APS). With four online experimental stations and various offline capabilities, HPCAT focused on providing synchrotron x-ray capabilities for high pressure temperature research supporting broad user community. Overall, array of online/offline described, including some recent developments remote support concomitant impact current pandemic. General overview work done...
Diamond-anvil cell experiments augmented by first-principles calculations have found a remarkable stability of the N(3-) ion in Li3N to sixfold volume reduction. A new (gamma) phase is discovered above 40(+/-5) GPa, with an 8% collapse and band gap quadrupling at transition determined synchrotron x-ray diffraction inelastic scattering. gamma-Li(3)N (Fm3m, Li(3)Bi-like structure) remains stable up 200 do not predict metallization until approximately 8 TPa. The high structural stability, wide...
As oxygen may occupy a major volume of oxides, densification amorphous oxides under extreme compression is dominated by reorganization during compression. X-ray Raman scattering (XRS) spectra for SiO_{2} glass up to 1.6 Mbar reveal the evolution heavily contracted environments characterized decrease in average O-O distance and potential emergence quadruply coordinated (oxygen quadcluster). Our results also that edge energies at centers gravity XRS features increase linearly with bulk...
The strongly correlated material FeSi displays several unusual thermal, magnetic, and structural properties under varying pressure–temperature (P–T) conditions. It is a potential thermoelectric alloy with geochemical implications as possible constituent at the Earth's core-mantle boundary (CMB). Previous theoretical studies predicted pressure-induced B20–B2 transition ambient temperature below 40 GPa; however, experimentally, observed only high P–T In this study, we have performed...
Inelastic x-ray scattering (IXS) of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:msub><a:mi mathvariant="normal">B</a:mi><a:mn>2</a:mn></a:msub><a:msub><a:mi mathvariant="normal">O</a:mi><a:mn>3</a:mn></a:msub></a:mrow></a:math> glass up to ∼2.2 Mbar reveals electronic bonding transitions in oxide glasses. B -edge IXS identifies the high-energy feature above ∼1.4 and a gradual increase its intensity toward Mbar, indicating formation hypervalent boron via electron...
Abstract The structural adaptation in MgSiO 3 melts under compression up to 130 GPa is the key revealing origins of pronounced negative buoyancy at core‐mantle boundary (CMB). A full understanding melt densification requires study pressure‐induced changes bonding configuration around oxygen CMB, which has proven be difficult measure. Here, experimental breakthrough O K ‐edge inelastic X‐ray scattering enables collection spectra glasses ~130 GPa, along with ab initio molecular dynamics...
Noncrystalline oxides under pressure undergo gradual structural modifications, highlighted by the formation of a dense noncrystalline network topology. The nature densified networks and their electronic structures at high pressures may account for mechanical hardening anomalous changes in electromagnetic properties. Despite its importance, direct probing amorphous compression above Mbar (>100 GPa) is currently lacking. Here, we report observation pressure-driven configurations delocalization...
Electronic states of iron in Earth's mantle minerals including ferropericlase, silicate perovskite, and post-perovskite have been previously investigated at high pressures and/or temperatures using various experimental techniques, X-ray emission Mössbauer spectroscopies. Although such methods used to infer changes the electronic spin valence lower minerals, they do not directly probe 3d quantitatively. Here we use 1s2p resonant spectroscopy (RXES) Fe K pre-edge assess crystal-field...
Using inelastic x-ray scattering techniques, we have succeeded in probing the high-pressure electronic structure of helium at 300 K. Helium has widest known valence-conduction band gap all materials a property whose response been inaccessible to direct measurements. We observed rich electron excitation spectrum, including cutoff edge above 23 eV, sharp exciton peak showing linear volume dependence, and series excitations continuum 26 45 eV. determined dispersion along Γ-M direction over two...
We report here pressure induced nanocrystal coalescence of ordered lead chalcogenide arrays into one-dimensional (1D) and 2D nanostructures. In particular, atomic crystal phase transitions mesoscale PbS PbSe nanocrystals have been observed monitored in situ respectively by wide- small-angle synchrotron X-ray scattering techniques. At the scale, both underwent reversible structural transformations from cubic to orthorhombic at significantly higher pressures than those for corresponding bulk...
Valence transition could induce structural, insulator-metal, nonmagnetic-magnetic and superconducting transitions in rare-earth metals compounds, while the underlying physics remains unclear due to complex interaction of localized $4f$ electrons as well their coupling with itinerant electrons. The valence elemental metal europium (Eu) still has remained a matter debate. Using resonant x-ray emission scattering diffraction, we pressurize states Eu study its structure up 160 GPa. We provide...
Metallization of hydrogen as a key problem in modern physics is the pressure-induced evolution electronic band from wide-gap insulator to closed gap metal. However, due its remarkably high energy, insulating has never before been directly observed under pressure. Using high-brilliance, high-energy synchrotron radiation, we developed an inelastic x-ray probe yield information situ pressures diamond-anvil cell. The dynamic structure factor was measured over large energy range 45 eV. found...
The detailed atomic structures of shock compressed basaltic glasses are not well understood. Here, we explore the silicate glass with a diopside–anorthite eutectic composition (Di 64 An 36 ), common Fe‐free model composition, using oxygen K‐edge X‐ray Raman scattering and high‐ resolution 27 Al solid‐state NMR spectroscopy report previously unknown details shock‐induced changes in configurations. A topologically driven densification Di is indicated by increase energy for upon compression....
We report the results of high pressure x-ray diffraction, absorption, and electrical transport measurements Kondo insulator Ce$_3$Bi$_4$Pt$_3$ up to 42 GPa, highest reached in study any Ce-based KI. observe a smooth decrease volume movement toward intermediate Ce valence with pressure, both which point increased electron correlations. Despite this, temperature-dependent resistance data show suppression interaction-driven ambient insulating ground state. also discuss potential ramifications...
Polyethylene (C2H4)n was compressed to pressures between 10 and 30 GPa in a diamond anvil cell (DAC) laser heated above 2500 K for approximately one second. This resulted the chemical decomposition of polymer into carbon hydrocarbon reaction products. After quenching ambient temperature, products were measured DAC at ranging from 29 using combination x-ray diffraction (XRD) small angle scattering (SAXS). XRD identified cubic methane as predominant product species with their pressure-volume...