Thomas Duffy

Thomas Duffy
Princeton University | PU · Department of Geosciences

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285
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Publications

Publications (285)
Article
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There has been considerable recent interest in the high-pressure behavior of silicon carbide, a potential major constituent of carbon-rich exoplanets. In this work, the atomic-level structure of SiC was determined through in situ X-ray diffraction under laser-driven ramp compression up to 1.5 TPa; stresses more than seven times greater than previou...
Article
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Mg 2 GeO 4 is important as an analog for the ultrahigh-pressure behavior of Mg 2 SiO 4 , a major component of planetary interiors. In this study, we have investigated magnesium germanate to 275 GPa and over 2,000 K using a laser-heated diamond anvil cell combined with in situ synchrotron X-ray diffraction and density functional theory (DFT) computa...
Preprint
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Combining an x-ray free electron laser (XFEL) with high power laser drivers enables the study of phase transitions, equation-of-state, grain growth, strength, and transformation pathways as a function of pressure to 100s GPa along different thermodynamic compression paths. Future high-repetition rate laser operation will enable data to be accumulat...
Article
The high-pressure behavior and polymorphism of gold have attracted strong recent interest from theory as well as from both static and dynamic experiments. In this study, gold was dynamically ramp-compressed to 690 GPa via laser ablation using the Omega Laser Facility (University of Rochester) in order to investigate the stability regions of this no...
Article
Full-text available
The discovery of an extraordinary number of extrasolar planets, characterized by an unexpected variety of sizes, masses and orbits, challenges our understanding of the formation and evolution of the planets in the Solar System and the perception of the Earth as the prototypical habitable world. Many exoplanets appear to be rocky and yet more massiv...
Article
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The response of forsterite, Mg₂SiO₄, under dynamic compression is of fundamental importance for understanding its phase transformations and high‐pressure behavior. Here, we have carried out an in situ X‐ray diffraction study of laser‐shocked polycrystalline and single‐crystal forsterite (a‐, b‐, and c‐orientations) from 19 to 122 GPa using the Matt...
Preprint
Full-text available
High-pressure phases of Mg$_2$GeO$_4$ have been explored as an analogue system for the ultra-high pressure behavior of Mg$_2$SiO$_4$. Using a laser-heated diamond anvil cell combined with in situ synchrotron X-ray diffraction, we have identified a novel phase in which germanium adopts eight-fold coordination with oxygen. The cubic Th3P4-type phase...
Conference Paper
In situ x-ray diffraction and wave-profile measurements were carried out on polycrystalline boron carbide under laser- induced shock compression at 51 GPa at the Matter in Extreme Conditions end-station of the Linac Coherent Light Source. The diffraction data indicate that boron carbide remains crystalline to this pressure and there is no evidence...
Article
The high-pressure behavior of metal dioxides, AO2 are of wide interest due to their extensive polymorphism. In this study, high-pressure phase transitions in dioxides of selected group 4 and 14 elements (SnO2, PbO2 and HfO2) were examined using in situ x-ray diffraction in the laser-heated diamond anvil cell and theoretical density functional theor...
Article
Neighborite, NaMgF3, is used as a model system for understanding phase transitions in ABX3 systems (e.g., MgSiO3) at high pressures. Here we report diamond anvil cell experiments that identify the following phases in NaMgF3 with compression to 162 GPa: NaMgF3 (perovskite) → NaMgF3 (post-perovskite) → NaMgF3 (Sb2S3-type) → NaF (B2-type) + NaMg2F5 (P...
Article
The behavior of silicon carbide (SiC) under shock compression is of interest due to its applications as a high-strength ceramic and for general understanding of shock-induced polymorphism. Here we use the Matter in Extreme Conditions beamline of the Linac Coherent Light Source to carry out a series of time-resolved pump-probe x-ray diffraction meas...
Article
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Dynamic-compression experiments on geological materials are important for understanding the composition and physical state of the deep interior of the Earth and other planets. These experiments also provide insights into impact processes relevant to planetary formation and evolution. Recently, new techniques for dynamic compression using high-power...
Article
The compression behavior of crystalline and amorphous germania holds considerable interest as an analog for silica and for understanding the structural response of AX2 compounds generally. In this paper, the α−PbO2-type and Pa3¯-type polymorphs of GeO2 were investigated under high pressure using angle-dispersive synchrotron x-ray diffraction in the...
Article
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In the version of this Letter originally published, in the Acknowledgements, the surname of M. Herrmann was misspelt as ‘Hermann’. This has now been corrected.
Article
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The recent discovery of thousands of planets outside our Solar System raises fundamental questions about the variety of planetary types and their corresponding interior structures and dynamics. To better understand these objects, there is a strong need to constrain material properties at the extreme pressures found within planetary interiors1,2. He...
Article
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The high-pressure behavior of germanates is of interest as these compounds serve as analogs for silicates of the deep Earth. Current theoretical and experimental studies of iron germanate, FeGeO3, are limited. Here, we have examined the behavior of FeGeO3 to 127 GPa using the laser-heated diamond anvil cell combined with in situ synchrotron X-ray d...
Article
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The high-pressure behavior of Fe alloys governs the interior structure and dynamics of super-Earths, rocky extrasolar planets that could be as much as 10 times more massive than Earth. In experiments reaching up to 1300 GPa, we combine laser-driven dynamic ramp compression with in situ x-ray diffraction to study the effect of composition on the cry...
Article
The effect of incorporation of Fe²⁺ on perovskite (Pbnm) and postperovskite (Cmcm) structures was investigated in the (Mg,Fe)GeO3 system. Addition of up to 22% Fe in the GdFeO3-type perovskite A-site leads to significant decrease in the phase transition boundary between perovskite and postperovskite, a decrease in octahedral tilting and compressibi...
Article
Molybdenum (Mo) is a transition metal with a wide range of technical applications. There has long been strong interest in its high-pressure behavior, and it is often used as standard for high-pressure experiments. Combining powder x-ray diffraction and dynamic ramp compression, structural and equation of state data were collected for solid Mo to 1...
Conference Paper
In this paper, we report recent progress in high-energy X-ray focusing by using Kirkpatrick-Baez (K–B) mirrors in combination with a sagittally bent Laue monochromator. This combination of optics provides a high flux X-ray beam, which can significantly reduce the data acquisition time for high-pressure pair distribution function (HP-PDF) measuremen...
Conference Paper
In this paper, we report recent development of the high-pressure pair distribution function (HP-PDF) measurement technique using a focused high-energy X-ray beam coupled with a diamond anvil cell (DAC). The focusing optics consist of a sagittally bent Laue monochromator and Kirkpatrick-Baez (K–B) mirrors. This combination provides a clean high-ener...
Conference Paper
In this paper, we report some recent developments of the diffraction-based absolute X-ray energy calibration method. In this calibration method, high spatial resolution of the measured detector offset is essential. To this end, a remotely controlled long-translation motorized stage was employed instead of the less convenient gauge blocks. It is fou...
Article
Lead fluoride, PbF2, was investigated experimentally in the laser-heated diamond anvil cell by x-ray diffraction to pressures of 75 GPa at room temperature and to 64.5 GPa and 2430 K, as well as through first-principles density functional theory calculations up to 70 GPa. During room temperature compression, no discontinuous changes in the x-ray di...
Article
Valence and spin states of Fe were investigated in a glass of almandine (Fe3Al2Si3O12) composition to 91 GPa by X-ray emission spectroscopy and energy- and time-domain synchrotron Mössbauer spectroscopy in the diamond-anvil cell. Changes in optical properties, total spin moment and Mössbauer parameters all occur predominantly between 1 bar and ~30...
Article
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We report development of micro-focusing optics for high-energy x-rays by combining a sagittally bent Laue crystal monchromator with Kirkpatrick-Baez (K-B) X-ray focusing mirrors. The optical system is able to provide a clean, high-flux X-ray beam suitable for pair distribution function (PDF) measurements at high pressure using a diamond anvil cell...
Chapter
Super-Earths are newly discovered extrasolar planets of approximately 1–10 Earth masses in size. They may span a wide range of possible compositions from Earth-like to those enriched in iron, water, or other constituents. Knowledge of the mineralogy of super-Earth planets is essential to understanding their interior structure, thermal behavior, and...
Article
Molybdenum (Mo) is a body-centered-cubic (bcc) transition metal that has widespread technological applications. Although the bcc transition elements are used as test cases for understanding the behavior of metals under extreme conditions, the melting curves and phase transitions of these elements have been the subject of stark disagreements in rece...
Article
The compressibility of nanocrystalline gold (n-Au, 20 nm) has been studied by x-ray total scattering using high-energy monochromatic x-rays in the diamond anvil cell under quasi-hydrostatic conditions up to 71 GPa. The bulk modulus, K 0, of the n-Au obtained from fitting to a Vinet equation of state is ~196(3) GPa, which is about 17% higher than fo...
Article
Yttrium iron garnet (YIG, Y3Fe5O12) was examined up to 74 GPa and 1800 K using synchrotron x-ray diffraction in a diamond anvil cell. At room temperature, YIG remained in the garnet phase until abrupt amorphization occurred at 51 GPa, consistent with earlier studies. Upon laser heating up to 1800 K, the material transformed to a single-phase orthor...
Article
High-pressure single-crystal X-ray diffraction experiments were conducted on natural cordierite crystals with composition Mg1.907(18)Fe0.127(6)Al4.01(2)Si4.96(3)Na0.026(3)O18.12(9) using a synchrotron X-ray source. The samples were compressed at 300 K in a diamond-anvil cell to a maximum pressure of 15.22(15) GPa with a neon pressure-transmitting m...
Article
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Angle-and energy-dispersive X-ray diffraction experiments in a radial geometry were performed in the diamond anvil cell on polycrystalline platinum samples at pressures up to 63 GPa. Observed yield strength and texture depend on grain size. For samples with 70-300-nm particle size, the yield strength is 5-6 GPa at ~60 GPa. Coarse-grained (~2-µm par...
Article
Single crystals of Mg0.9Fe0.1SiO3 orthopyroxene were compressed to 48.5 GPa in a Ne pressure-transmitting medium.•Transformation to the previously reported high-pressure β-orthopyroxene (β-opx) phase, as well as to two new high-pressure phases, was observed.•The new phases have been named α- and β-post-orthopyroxene (α-popx and β-popx) and both hav...
Article
We report a pressure-induced dense tetrahedral intermediate state via Ge–O–Ge rotation formed at 3–5 GPa and the polyhedral relations in GeO2 glass up to 17.5 GPa using in situ X-ray total scattering and X-ray absorption (XAFS) techniques. It was found that the nearest-neighbor Ge-Ge correlations show a decrease reaching a minimum between 4 and 6 G...
Article
Full-text available
Laser-based dynamic compression provides new opportunities to study the structures and properties of materials to ultrahigh pressure conditions. In this technique, high-powered laser beams are used to ablate a sample surface and by reaction a compression wave is generated and propagate through the sample. By controlling the shape and duration of th...
Article
Full-text available
The recent discovery of more than a thousand planets outside our Solar System, together with the significant push to achieve inertially confined fusion in the laboratory, has prompted a renewed interest in how dense matter behaves at millions to billions of atmospheres of pressure. The theoretical description of such electron-degenerate matter has...
Article
Full-text available
Single-crystal magnesium oxide (MgO) samples were ramp compressed to above 200 GPa pressure at the Omega laser facility. Multi-stepped MgO targets were prepared using lithography and wet etching techniques. Free surface velocities of ramp-compressed MgO were measured with a VISAR. The sound velocity and stress-density response were determined using...
Article
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Recent experimental measurements of the equation of state of perovskites and post-perovskites in the (Mg,Fe)SiO3 and (Mg,Fe,Al)(Fe,Al,Si)O3 systems over a wide range of iron contents are used to constrain the effects of Fe and Al on density and bulk modulus of these phases at deep mantle pressures. The density of Fe-bearing perovskite follows a lin...
Article
Polycrystalline ruby (α-Al2O3:Cr3+), a widely used pressure calibrant in high-pressure experiments, was compressed to 68.1 GPa at room temperature under non-hydrostatic conditions in a diamond anvil cell. Angle-dispersive X-ray diffraction experiments in a radial geometry were conducted at beamline X17C of the National Synchrotron Light Source. The...
Article
Full-text available
Brillouin spectroscopy is an optical technique that allows one to determine the directional dependence of acoustic velocities in minerals and materials subject to a wide range of environmental conditions. It is based on the inelastic scattering of light by spontaneous collective motions of particles in a material in the frequency range between 10−2...
Article
The six independent elastic constants (C11, C12, C13, C33, C44, and C66) of single-crystal MgF2 in the rutile structure have been measured by Brillouin spectroscopy at room temperature from ambient conditions to 7.4 GPa. Measurements were performed on two monocrystals with perpendicular faces, (001) and (100). A quasi-linear fit from finite strain...
Article
The equation of state and compression behavior of lithium fluoride, LiF, have been determined to 92 GPa by X-ray diffraction in a diamond anvil cell. A neon pressure-transmitting medium was used to minimize the effect of differential stress on the sample. Consistent results using multiple pressure standards were obtained. By fitting the pressure–vo...
Article
Full-text available
Forsterite, Mg2SiO4, the magnesian end-member of the olivine system, is the archetypal example of an orthosilicate structure. We have conducted synchrotron-based single-crystal X-ray diffraction experiments to 90 GPa on synthetic end-member forsterite to study its equation of state and phase transitions. Upon room-temperature compression, the forst...
Article
Full-text available
Iron was ramp-compressed over timescales of 3 ≤ t(ns) ≤ 300 to study the time-dependence of the α→ε (bcc→hcp) phase transformation. Onset stresses σα→ε for the transformation ∼14.8-38.4 GPa were determined through laser and magnetic ramp-compression techniques where the transition strain-rate was varied between 106≤μ˙α→ε(s-1) ≤ 5×108. We find σα→ε=...
Article
The structural behavior of GeO2 glass has been investigated up to 64 GPa using results from x-ray absorption spectroscopy in a diamond anvil cell combined with previously reported density measurements. The difference between the nearest Ge-O distances of glassy and rutile-type GeO2 disappears at the Ge-O distance maximum at 20 GPa, indicating compl...
Article
It is well known that anelasticity has significant effects on the propagation of seismic waves, as manifested by physical dispersion and dissipation. Investigations of anelasticity provide complementary constraints on the physical properties of Earth materials, but — contrary to imaging with elastic waves — progress in mapping Earth's anelasticity...
Article
Full-text available
Magnesium oxide is an important component of the Earth's mantle and has been extensively studied at pressures and temperatures relevant to Earth. However, much less is known about the behaviour of this oxide under conditions likely to occur in extrasolar planets with masses up to 10 times that of Earth, termed super-Earths, where pressures can exce...
Article
Multiple thickness Fe foils were ramp compressed over several nanoseconds to pressure conditions relevant to the Earth's core. Using wave-profile analysis, the sound speed and the stress-density response were determined to a peak longitudinal stress of 273 GPa. The measured stress-density states lie between shock compression and 300-K static data,...
Article
Full-text available
Although coupling the X-ray absorption fine structure (XAFS) technique to the diamond anvil cell (DAC) has long been recognized as potentially important for understanding the behavior and evolution of the local and electronic structure of matter under extreme conditions, the DAC has been regarded as poorly suited for XAFS due to the DAC imposed gli...
Article
The laser-heated diamond cell has been improved with the integration of in-situ X ray microprobe and double hot-plate heating techniques. A multimode YAG laser provides a flat-top power distribution at the focal spot. A hot-plate configuration is created where the heat generation and temperature measurement are concentrated at the planar interface...
Article
Fe-rich natural orthopyroxenes with compositions of (Mg0.61Fe0.38Ca0.01)SiO3 (Fe#38) and (Mg0.25Fe0.74Ca0.01)SiO3 (Fe#74) were studied at pressures up to 155GPa and temperatures up to 3000K. Single-phase orthorhombic GdFeO3-type perovskite was synthesized by heating to ~2000 K at 63GPa for the Fe#38 composition and at 72GPa for the Fe#74 compositio...
Article
Robert Cooper Liebermann received the 2012 Edward A. Flinn III Award at the AGU Fall Meeting Honors Ceremony, held on 5 December 2012 in San Francisco, Calif. The award honors “individuals who personify the Union's motto ‘unselfish cooperation in research’ through their facilitating, coordinating, and implementing activities.”
Article
Natural and synthetic pyrope–almandine compositions from 38 to 100 mol% almandine (Alm38–Alm100) were studied by synchrotron X-ray diffraction in the laser-heated diamond anvil cell to 177 GPa. Single-phase orthorhombic GdFeO3-type perovskites were synthesized across the entire examined compositional range at deep lower mantle pressures, with highe...
Article
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We have performed a series of co-compression experiments on Au, Pt, Mo, MgO and NaCl to extend internally consistent pressure calibration and characterize shear strength of pressure media to 2.5 Mbar. Measured unit cell volumes of calibrants show differences between existing pressure scales of ˜10% above 2 Mbar. A new comprehensive pressure scale i...
Article
The compression behavior and stress state of nanocrystalline tungsten boride (WB) were investigated using radial x-ray diffraction (RXRD) in a diamond-anvil cell under non-hydrostatic compression up to 60.4 GPa. The compression properties and stress state are analyzed using lattice strain theory. Experiments were conducted at beamline X17C of the N...
Article
In this paper, we report a method of precise and fast absolute x-ray energy calibration over a wide energy range using an iterative x-ray diffraction based method. Although accurate x-ray energy calibration is indispensable for x-ray energy-sensitive scattering and diffraction experiments, there is still a lack of effective methods to precisely cal...
Article
To understand the effect of hydration on the sound velocities of major mantle minerals and to constrain the mantle's H 2 O budget, we have measured the single-crystal elastic moduli of hydrous ringwoodite, (Mg 1.633 Fe 2 + 0.231 Fe 3 + 0.026)Si 1.00 H 0.179 O 4 with 1.1 wt.% H 2 O using Brillouin scattering combined with X-ray diffraction in an ext...
Article
The formation and properties of the post-perovskite (CaIrO3-type) phase were studied in Fe-rich compositions along the pyrope–almandine ((Mg,Fe)3Al2Si3O12) join. Natural and synthetic garnet starting materials with almandine fractions from 38 to 90 mol% were studied using synchrotron X-ray diffraction in the laser-heated diamond anvil cell. Single-...
Article
Ringwoodite is expected to be an abundant mineral in the Earth's transition zone from 520 to 660-km depth. Previous studies showed that ringwoodite can incorporate more than 1 wt.% H2O at the pressure-temperature (P-T) conditions of the region. Most importantly, the presence of water can significantly affect the elasticity of ringwoodite. Laborator...
Article
Seismic tomography has characterized dense large low shear velocity provinces (LLVSPs) and ultra-low velocity zones (ULVZs) at the base of the Earth's lower mantle. The morphology and seismic properties of these regions indicate that chemical heterogeneity plays a major role in these features. It is therefore important to characterize how Fe enrich...
Article
The role of geologic collections has diminished over the years as new technology has lead to emphasis on computer based modeling and theoretical work in the geosciences. Mineralogy and petrology tend to be thought of as mature sciences, and many departments are cutting back or eliminating courses in these subjects. Collections that accompany instru...
Article
The laser heated diamond anvil cell technique can readily achieve the pressure and temperature domain of Earth from upper mantle to outer core. The laser heating diamond anvil cell X-ray facilities (X17-DAC), consists of X17B3 and X17C stations on a superconducting wiggler beamline and a sample preparation/spectroscopy laboratory at the National Sy...
Article
Accurate pressure measurements are essential for experimental measurements of phase transitions and physical properties of materials under conditions of the Earth's deep interior. Pressure scales based upon shock compression experiments suffer from uncertainties at high compressions due to corrections for thermal effects. Independent pressure scale...
Article
A fine marriage between seismic data and laboratory experiments carried out at the extreme conditions of Earth's deep interior indicates that the planet's liquid outer core is poor in oxygen. See Letter p.513
Article
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The Raman spectra of bixbyite, Mn2O3, were measured up to 40 GPa at room temperature. Mn2O3 undergoes a phase transition from the C-type rare earth structure to the CaIrO3-type (post-perovskite) structure at 16-25 GPa. The transition pressure measured in Raman spectroscopy is significantly lower than the pressure reported previously by an X-ray dif...
Article
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The single-crystal elastic properties of Fe-bearing wadsleyite with 1.93 wt% HâO (Mg{sub 1.634}Fe{sub 0.202}H{sub 0.305}SiOâ) have been determined by Brillouin scattering. At ambient conditions, the aggregate bulk and shear moduli (K{sub S0}, Gâ) of this wadsleyite are 156.2(5) and 98.0(3) GPa, respectively. Compared to the corresponding anhydrous...