A5034101539- High-pressure geophysics and materials
- Geological and Geochemical Analysis
- Diamond and Carbon-based Materials Research
- earthquake and tectonic studies
- Astro and Planetary Science
- Planetary Science and Exploration
- Geomagnetism and Paleomagnetism Studies
- Stellar, planetary, and galactic studies
- Crystal Structures and Properties
- Electronic and Structural Properties of Oxides
- Boron and Carbon Nanomaterials Research
- Advanced materials and composites
- Semiconductor materials and devices
- Advanced ceramic materials synthesis
- Energetic Materials and Combustion
- Metal and Thin Film Mechanics
- Metallurgical Processes and Thermodynamics
- Geology and Paleoclimatology Research
- Laser-Plasma Interactions and Diagnostics
- Atmospheric Ozone and Climate
- Fiber-reinforced polymer composites
- Advanced Condensed Matter Physics
- Graphene research and applications
- Laser-induced spectroscopy and plasma
- Graphite, nuclear technology, radiation studies
United States Coast Guard Academy
2022-2024
Planetary Science Institute
2002-2022
Lawrence Livermore National Laboratory
2013-2022
Yale University
2012-2021
University of California, Berkeley
2002-2021
New Mexico State University
2006-2011
Whitney Museum of American Art
2011
Purdue University West Lafayette
2009
University of Bayreuth
2006-2008
California Institute of Technology
2004-2006
Recently, sophisticated theoretical computational studies have proposed several new crystal structures of carbon (e.g., bct-C4, H-, M-, R-, S-, W- and Z-carbon). However, until now, there lacked experimental evidence to verify the predicted high-pressure for cold-compressed elemental at least up 50 GPa. Here we present direct that this enigmatic structure is currently only consistent with M-carbon, one structures. Furthermore, show phase transition extremely sluggish, which led observed...
Terrestrial planets in the solar system, such as Earth, are oxygen-rich, with silicates and iron being most common minerals their interiors. However, true chemical diversity of rocky orbiting other stars is yet unknown. Mass radius measurements used to constrain interior compositions super-Earths (exoplanets masses 1 - 10 Earth masses), typically interpreted planetary models that assume Earth-centric oxygen-rich compositions. Using models, super-Earth 55 Cancri e (mass 8 masses, 2 radii) has...
Significance Carbon is critical to life on Earth, climate regulation, and many geological processes. Despite its importance, the amount of carbon in planet has been poorly understood due uncertainty composition Earth’s core, likely largest reservoir carbon. Here, we demonstrate that becomes increasingly compatible silicate compared metal at high pressures temperatures which core formed. Therefore, can only be present low abundances, although still holds vast majority planet’s
Abstract Magma oceans were once ubiquitous in the early solar system, setting up initial conditions for different evolutionary paths of planetary bodies. In particular, redox magma may have profound influence on state subsequently formed mantles and overlying atmospheres. The relevant buffering reactions, however, remain poorly constrained. Using first-principles simulations combined with thermodynamic modeling, we show that Earth, Mars, Moon are likely characterized a vertical gradient...
Materials can be experimentally characterized to terapascal pressures by sending a laser-induced shock wave through sample that is precompressed inside diamond-anvil cell. This combination of static and dynamic compression methods has been demonstrated ultimately provides access the 10- 100-TPa (0.1-1 Gbar) pressure range relevant planetary science, testing first-principles theories condensed matter, studying new regime chemical bonding.
Using high-resolution synchrotron x-ray powder diffraction we have investigated the structural phase transitions and equations of state titanium dioxide $({\text{TiO}}_{2})$ under high pressure before after heating at temperature. The sequence observe experimentally is as follows: rutile $(\text{RT})\ensuremath{\rightarrow}\text{columbite}\text{ }(\text{CB})\ensuremath{\rightarrow}\text{baddeleyite}\text{ }(\text{MI})\ensuremath{\rightarrow}\text{orthorhombic}\text{ }\text{I}\text{...
Slippery When Squeezed The behavior of seismic waves as they pass through Earth's interior depends on the physical properties major mineral phases at depth. If such minerals are anisotropic—that is, influence preferentially depending crystallographic orientation—interpreting structure a region becomes more challenging. In lowermost mantle, near boundary with outer core, deformation MgSiO 3 post-perovskite may affect anisotropy. Miyagi et al. (p. 1639 ) solved previous experimental...
The optical reflectance of a strong shock front in water increases continuously with pressure above 100 GPa and saturates at ∼45% 250 GPa. This is the first evidence electronic conduction high water. In addition, Hugoniot equation state up to 790 (7.9 Mbar) determined from velocity measurements made by detecting Doppler shift reflected light. From fit data we find that an mobility gap ∼2.5 eV controls thermal activation carriers pressures range 100–150 suggests contributes significantly...
We use high-resolution synchrotron x-ray powder diffraction and density-functional theory (DFT) to investigate the phase stability, equations of state (EOSs), mechanical hardness zirconia $({\text{ZrO}}_{2})$ up $\ensuremath{\sim}54$ 160 GPa, respectively. For equilibrium at ambient conditions (MI), we provide an experimental EOS that is comparable results obtained from room-pressure Brillouin scattering experiments bulk modulus-volume systematics but different previous high-pressure...
Abstract Magnesium oxide (MgO) is a significant component of planetary interiors, particularly Earth's mantle and other rocky planets within beyond our solar system; thus its high‐pressure, high‐temperature behavior important to understanding the thermochemical evolution planets. Laser‐heated diamond‐anvil cell (DAC) experiments on (Mg,Fe)O ferropericlase up ~40 GPa show that previous DAC MgO melting are too low, while multi‐anvil yield temperatures high. Instead, quasi‐static experimental...
We measure the onset of decomposition silicon carbide, SiC, to and carbon (e.g., diamond) at high pressures temperatures in a laser-heated diamond-anvil cell. identify through x-ray diffraction multiwavelength imaging radiometry coupled with electron microscopy analyses on quenched samples. find that B3 SiC (also known as 3C or zinc blende SiC) decomposes temperatures, following phase boundary negative slope. The high-pressure measured are considerably lower than those ambient, our...
Laser-driven shock compression of samples precompressed to 1 GPa produces high-pressure-temperature conditions inducing two significant changes in the optical properties water: onset opacity followed by enhanced reflectivity initially transparent water. The at infrared wavelengths can be interpreted as a semiconductor<-->electronic conductor transition water, and is found pressures above approximately 130 for single-shocked GPa. Our results indicate that conductivity deep interior "icy"...
Using high-resolution synchrotron powder x-ray diffraction, we have investigated the stability and equation of state (EOS) hafnia ${\text{HfO}}_{2}$ phases under high pressures before after laser heating to temperatures. We observe three with increasing pressure: baddeleyite (monoclinic, MI), orthorhombic I (OI), cotunnite (orthorhombic, OII). The OII phase is stable up a pressure at least 105 GPa $\ensuremath{\sim}1800$ $(\ifmmode\pm\else\textpm\fi{}200)\text{ }\text{K}$. provide...
Convection provides the mechanism behind plate tectonics, which allows oceanic lithosphere to be subducted into mantle as "slabs" and new rock generated by volcanism. Stagnation of subducting slabs deflection rising plumes in Earth's shallow lower have been suggested result from a viscosity increase at those depths. However, for this remains elusive. Here, we examine melting behavior MgO-FeO binary system high pressures using laser-heated diamond-anvil cell show that liquidus solidus (Mg x...
Here, we couple two-dimensional, 4-color multi-wavelength imaging radiometry with laser flash heating to determine temperature profiles and melting temperatures under high pressures in a diamond-anvil cell. This technique combines the attributes of (e.g., minimal chemical reactions, thermal runaway, sample instability), those 2D mapping reduction chromatic aberrations). Using this new conjunction electron microscopy makes powerful tool at generated by
Abstract The origin of Earth's ancient magnetic field is an outstanding problem. It has recently been proposed that exsolution MgO from the core may provide sufficient energy to drive early geodynamo. Here we present new experiments on Mg partitioning between iron‐rich liquids and silicate/oxide melts. Our results indicate depends strongly oxygen content in liquid, contrast previous findings it only temperature. Consequently, during cooling drastically reduced insufficient geodynamo alone....
We explore the stability of ambient pressure zinc-blende polymorph (B3) structure silicon carbide (SiC) at high pressures and temperatures where it transforms to rocksalt (B1) structure. find that transition occurs \ensuremath{\sim}40 GPa lower than previously measured when heated moderately temperatures. A is consistent with predicted in numerous ab initio computations. a large volume decrease across \ensuremath{\sim}17%, drop increasing higher formation pressures, suggesting this driven...
Using high-resolution, synchrotron-based powder X-ray diffraction (XRD), we have studied the high-pressure behavior of anatase phase nanocrystalline TiO2 (nc-TiO2) under hydrostatic conditions. We find that for with a grain size larger than ∼40 nm, room-pressure bulk modulus K0 remains constant at ∼200 GPa to within experimental uncertainties. An ∼15% decrease in is observed grains are ∼20 nm and unchanged down 6 diameter, indicating rapid increase compressibility nc-TiO2 between 40 20 nm.
In situ temperature measurements in laser-heated diamond-anvil cells (LHDACs) are among the most fundamental experiments undertaken high-pressure science. Despite its importance, few efforts have been made to examine alteration of thermal radiation spectra hot samples by wavelength-dependent absorption sample itself and gradients within their influence on while laser heating. this study, we take (Mg, Fe)O ferropericlase as an example evaluate effects these two factors. Iron-rich shows strong...
Seismic observations suggest that the uppermost region of Earth's liquid outer core is buoyant, with slower velocities than bulk core. One possible mechanism for formation a stably stratified layer immiscibility in molten iron alloy systems, which has yet to be demonstrated at pressures. We find between Fe-Si and Fe-Si-O persisting least 140 GPa through combination laser-heated diamond-anvil cell experiments first-principles molecular dynamics simulations. High-pressure system may explain...
Abstract The recent JWST detections of carbon-bearing molecules in a habitable-zone sub-Neptune have opened new era the study low-mass exoplanets. regime spans wide diversity planetary interiors and atmospheres not witnessed solar system, including mini-Neptunes, super-Earths, water worlds. Recent works investigated possibility gas dwarfs, with rocky thick H 2 -rich atmospheres, to explain aspects population, radius valley. Interactions between envelope potential magma ocean may lead...
High‐resolution x‐ray diffraction provides evidence that potassium (K) alloys with iron (Fe) when the two pure elements are heated together at pressures above ∼26 gigapascals (GPa). Increases of 2–3% in volume ε (hexagonal close packed: hcp) high‐pressure phase Fe can be attributed to incorporation ∼1 atomic% (∼7000 ppm by weight) K into Fe. Our results provide experimental support for predictions, derived from quantum mechanical calculations, pressure induce alloying due a change...