A5085730573- High-pressure geophysics and materials
- Nuclear Physics and Applications
- Advanced Chemical Physics Studies
- Quantum, superfluid, helium dynamics
- Crystallography and molecular interactions
- Methane Hydrates and Related Phenomena
- Inorganic Fluorides and Related Compounds
- Hydrogen Storage and Materials
- Diamond and Carbon-based Materials Research
- Nuclear Materials and Properties
- Radiation Detection and Scintillator Technologies
- Boron and Carbon Nanomaterials Research
- Radiation Therapy and Dosimetry
- Spectroscopy and Quantum Chemical Studies
- SAS software applications and methods
- Electronic and Structural Properties of Oxides
- Thermal and Kinetic Analysis
- Chalcogenide Semiconductor Thin Films
- Inorganic Chemistry and Materials
- Electron and X-Ray Spectroscopy Techniques
- Crystal Structures and Properties
- 2D Materials and Applications
- Hydrocarbon exploration and reservoir analysis
- Geological and Geochemical Analysis
- Semiconductor materials and devices
Oak Ridge National Laboratory
2020-2023
University of California, Riverside
2022
Arizona State University
2022
Tohoku University
2022
Center for High Pressure Science and Technology Advanced Research
2018-2022
University of Edinburgh
2014-2018
Earth-abundant antimony trisulfide (Sb
We present full in situ structural solutions of carbon dioxide hydrate-II and hydrogen hydrate C0 at elevated pressures using neutron X-ray diffraction. find both hydrates adopt a common water network structure. The structure exhibits several features not previously found hydrates; most notably it is chiral has large open spiral channels along which the guest molecules are free to move. It that unrelated any experimentally known ice, silica, or zeolite but instead related two Zintl...
Transition-metal nitrides have applications in a range of technological fields. Recent experiments shown that new nitrogen-bearing compounds can be accessed through combination high temperatures and pressures, revealing richer chemistry than was previously assumed. Here, we show at pressures above 50 GPa greater 1500 K elemental copper reacts with nitrogen, forming diazenide (CuN2). Through synchrotron X-ray diffraction first-principles calculations explored the stability electronic...
Diamond and graphite are fundamental sources of carbon in the upper mantle, their reactivity with H2-rich fluids present at these depths may represent key to unravelling deep abiotic hydrocarbon formation. We demonstrate an unexpected high between carbons' most common allotropes, diamond graphite, hydrogen conditions comparable those Earth's mantle along subduction zone thermal gradients. Between 0.5-3 GPa temperatures as low 300 °C, reacts readily H2 yielding methane (CH4), whilst higher...
Through a series of x-ray diffraction, optical spectroscopy diamond anvil cell experiments, combined with density functional theory calculations, we explore the dense CH_{4}-H_{2} system. We find that pressures as low 4.8 GPa can stabilize CH_{4}(H_{2})_{2} and (CH_{4})_{2}H_{2}, latter exhibiting extreme hardening intramolecular vibrational mode H_{2} units within structure. On further compression, unique structural composition, (CH_{4})_{3}(H_{2})_{25}, emerges. This novel structure holds...
In situ high-pressure high-temperature X-ray powder diffraction studies of the cobalt-hydrogen system reveal direct synthesis both binary cobalt hydride (CoH) and a novel dihydride (CoH2). We observe formation fcc CoH at pressures 4 GPa, which persists to 45 GPa. At this pressure, we see emergence with time further expanded lattice, identify as CoH2, where hydrogen atoms occupy tetrahedral vacancies. have explored alternative routes CoH2 can lower pressure 35 GPa by application high...
Abstract Diatomic elemental solids are highly compressible due to the weak interactions between molecules. However, as density increases intra- and intermolecular distances become comparable, leading a range of phenomena, such structural transformation, molecular dissociation, amorphization, metallisation. Here we report, following crystallization chlorine at 1.15(30) GPa into an ordered orthorhombic structure ( oC 8), existence mixed-molecular mC 8, 130(10)–241(10) GPa) concomitant...
As artificial diamond becomes more cost effective it is likely to see increasing use as a window for sample environment equipment used in diffraction experiments. Such windows are particularly useful they exhibit exceptional mechanical properties addition being highly transparent both X-ray and neutron radiation. A key application high-pressure studies, where anvil cells (DACs) access extreme conditions. However, despite their utility, an important consideration when using single-crystal...
Through a series of Raman spectroscopy studies, we investigate the behavior hydrogen-helium and hydrogen-nitrogen mixtures at high pressure across wide range concentrations. We find that there is no evidence chemical association or increased miscibility hydrogen helium in solid state up to pressures 250 GPa 300 K. In contrast, observe formation concentration-dependent N_{2}-H_{2} van der Waals solids, which react form N-H bonded compounds above 50 GPa. this combined study, can demonstrate...
The disordered-molecular-alloy phase (DMA) of ammonia hydrates [J. S. Loveday and R. J. Nelmes, Phys. Rev. Lett. 83, 4329 (1999)] is unique in that it has substitutional disorder water over the molecular sites a body centred cubic lattice. Whilst this structure been observed di- mono-hydrate compositions, not conclusively hemihydrate system. This work presents investigations structural behaviour as function P T. indications earlier studies [Ma et al. RSC Adv. 2, 4290 (2012)] DMA could be...
In situ high-pressure high-temperature synchrotron x-ray diffraction studies of the nickel-hydrogen system reveals synthesis a nickel polyhydride, ${\mathrm{Ni}}_{2}{\mathrm{H}}_{3}$. We observe formation NiH at pressures above 1 GPa, which remains stable to 52 GPa room temperature. Laser heating 1000 K this pressure initiates transition phase we determine as ${\mathrm{Ni}}_{2}{\mathrm{H}}_{3}$, crystallizing in body-centered monoclinic unit cell. The ${\mathrm{Ni}}_{2}{\mathrm{H}}_{3}$ was...
Three concepts for the application of multi-extreme conditions under in situ neutron scattering are described here. The first concept is a diamond anvil cell made from non-magnetic alloy. It shrunk size to fit existing magnets and future magnet designs designed best pressure stability upon cooling. This will allow maximum pressures above 10 GPa be applied simultaneously with (steady-state) high magnetic field (ultra-)low temperature. Additionally, an implementation miniature coils cells...
The hydrogen water system has been extensively studied above 0.5 GPa and below 0.2. We present neutron diffraction studies in the intermediate pressure range.
Hydrogen chemistry at extreme pressures is currently subject to extensive research due the observed and predicted enhanced physical properties when hydrogen incorporated in numerous binary systems. Despite high reactivity of hydrogen, noble metals (Cu, Ag, Au) display an outstanding resilience hydride formation, with no reports a stable compound molar ratio ≥ 1 room temperature. Here, through compression situ laser heating pure copper atmosphere, we explore affinity these elements adopt...
Hydrogen bond networks play a crucial role in biomolecules and molecular materials such as ices. How these react to pressure directs their properties at extreme conditions. We have studied one of the simplest hydrogen formers, chloride, from crystallization metallization, covering range more than 2.5 million atmospheres. Following symmetrization, we identify previously unknown phase by appearance new Raman modes changes x-ray diffraction patterns that contradict previous predictions. On...
When compressed in a matrix of solid hydrogen, many metals form compounds with increasingly high hydrogen contents. At density, hydrogenic sublattices can emerge, which may act as low-dimensional analogues atomic hydrogen. We show that at pressures and temperatures, ruthenium forms polyhydride species exhibit intriguing substructures counterintuitive electronic properties. Ru3H8 is synthesized from RuH H2 50 GPa temperatures excess 1000 K, adopting cubic structure short H–H distances....
High-pressure neutron diffraction is an extremely useful technique in the quest for making and understanding novel hydride superconductors. Neutron can be used to directly determine elemental stoichiometries atomic positions of many light elements such as hydrogen or deuterium, even presence heavy rare-earth metals. Here, we report on current status ongoing developments high-pressure superconductors other metal hydrides with a special focus advancements at Spallation Neutrons Pressure (SNAP)...
Mixtures of ammonia and water are major components the ``hot ice'' mantle regions icy planets. The ammonia-rich hemihydrate (AHH) plays a pivotal role as it precipitates from water-rich mixtures under pressure. It has been predicted to form ionic high-pressure structures, with fully disintegrated molecules. Utilizing Raman spectroscopy measurements up 123 GPa first-principles calculations, we report spontaneous ionization AHH compression. Spectroscopic reveal that molecular begins transform...
Urea, like many network forming compounds, has long been known to form inclusion (guest-host) compounds. Unlike other formers water, urea is not such compounds with simple molecules hydrogen. Such if they existed would be of interest both for the fundamental insight provide into molecular bonding and as potential gas storage systems. Urea proposed a hydrogen material [T. A. Strobel et al., Chem. Phys. Lett. 478, 97 (2009)]. Here, we report results high-pressure neutron diffraction studies D2...
Abstract Wavelength-dependent or hyperspectral imaging is a novel nondestructive characterization technique in the field of neutron radiography and computed tomography. A dedicated facility named VENUS currently being built at Oak Ridge National Laboratory to provide these capabilities for academia, industry, other national laboratories. This feature article describes materials science engineering, provides quick overview modes access facility, illustrates measurements interpretation results.
The chalcogens are known to react with one another form interchalcogens, which exhibit a diverse range of bonding and conductive behavior due the difference in electronegativity between group members. Through series high-pressure diamond anvil experiments combined density functional theory calculations, we report synthesis an S–Se hydride. At pressures above 4 GPa observe formation single solid composed both H2Se H2S molecular units. Further compression hydrogen medium leads alloyed compound...
Molecular hydrogen (H 2 ) has been proposed as an alternative fuel source for vehicles. Though H many benefits, such clean combustion and the highest known energy density by mass, there are issues in how to store it a safe cost effective way. One solution is chemical compound, gas clathrates (crystalline inclusion compounds) have shown promising results. Pressure provides powerful means tune properties of compounds its effects on potential storage materials widely explored. We recently...
Microchannel plates (MCPs) with a quad Timepix3 readout have emerged as promising neutron imaging camera for time-of-flight (TOF) capability. The detector comprises pair of chevron-stacked MCPs coupled to in vacuum enclosure. To make the neutron-sensitive, one is doped absorbers such <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> B and xmlns:xlink="http://www.w3.org/1999/xlink">nat</sup> Gd. data-driven zero-suppressed readout. Each...
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