High-Pressure Strength Study on Composite Material |
| Arslan K. Akhmetov Department of Earth Sciences, University of Western Ontario, London, ON, Canada N6A 5B7 aakhmeto@uwo.ca Sean R. Shieh Boris Kiefer (New Mexico State University) Thomas S. Duffy (Princeton University) |
| Facility: NSLS-X17C (DAC) Format: Poster |
| Knowledge of plastic properties of mantle materials under high pressures is of central importance for understanding dynamic processes within the mantle. The strength study of MgO and NaCl mixture (volume ratio 1:4) has been performed under non-hydrostatic conditions in a diamond anvil cell up to 55.5 GPa at room temperature utilizing radial energy dispersive X-ray diffraction technique. NaCl B1 phase undergoes a pressure-induced transformation to B2 phase at 30.2(±0.5) GPa, which is in a good agreement with previous studies. The strength weakening of NaCl appears near B1-B2 transition, decreasing the differential stress by a factor of more than 2.5, from 0.55(17) GPa to 0.19(4) GPa. For NaCl B1 phase, the differential stress component t (lower bound for the yield strength) is consistent with earlier studies and can be described by t=0.0244P-0.1367 where t and P is the pressure in GPa. The differential stress in NaCl B2 phase over the pressure range from 30.2?55.5 GPa can be described by t=0.0833P-2.3850, reaching 2.2 GPa at maximum applied pressure. The differential stress supported by MgO increases drastically but appeared to saturate at around 1.7 GPa under applied pressure of 20 GPa. However, it seems to be affected by the NaCl B1-B2 transition, we observe continuous increase of the differential stress component within MgO sample, which eventually reaches 3.5(1.0) GPa at maximum applied pressure of 55.5 GPa. |
Thermoelasticity of Fe2SiO4 composition at P, T conditions of the mid-mantle |
| Matt M Armentrout UCLA armentrout@ucla.edu Abby Kavner |
| Facility: APS-GSECARS Format: Poster |
| The goal of our research is to better characterized the phase stability and thermoelastic properties of the Fe2SiO4 assemblages at pressures and temperatures of the mid to deep mantle. In situ high pressure and high temperature experiments were conducted at GSECARS at the Advanced Photon Source over the pressure and temperature ranges of 9-62 GPa and 300-2500 K. Phase stability: In agreement with previous studies, we observe olivine Fe2SiO4 composition transforms to the spinel structure at 6 GPa, and the breakdown of the spinel structure to oxides before 31 GPa. Under further compression and at high temperature (~2000 K), the diffraction peaks for wustite disappear between 38 and 40 GPa and stishovite peaks disappear between 40 and 42 GPa. This disappearance coincides with the arrival of several new diffraction peaks at 40 and 42 GPa. Although the phase (or phases) are currently unidentified, we provide some constraints on behavior by presenting linear compressibility and thermal expansivity of observed lattice planes. This information on the Fe end member silicate will help fill out the Fe-rich portion of the lower mantle phase diagram, with possible implications for core-mantle interactions. Thermoelasticity: In addition to phase stability studies, we examined the density as a function of pressure and temperature for the ringwoodite, wustite, and stishovite phases. Using a simple thermal equation of state model, we determine a room pressure thermal expansion parameter for Fe-Ringwoodite to be equal to 1.28 ± 0.1 E-5 K-1, and wustite of 2.09 ± 0.43 E-5 K-1. This data will ultimately be used to help constrain the effect of iron concentration on seismic tomography of the transition zone and lower mantle. |
Pressure and Temperature Effects on Molybdenum Metal-Silicate Partitioning: Implications for Core Formation |
| Laura K Burkemper Institute of Meteoritics, University of New Mexico burkeml@unm.edu Carl B. Agee |
| Facility: Other Format: Poster |
| The moderately siderophile element molybdenum is depleted in the Earth?s mantle, relative to chondritic meteorites, due to core formation ? possibly within a primordial magma ocean. In order to understand the partitioning behavior of molybdenum as a function of pressure and temperature, we examined metal-silicate partitioning experiments over a temperature and pressure range of 1360-2080 oC and 0.5-11.5 GPa, respectively. Eight different silicate starting compositions were examined and D(Mo) was found to decrease with increasing pressure and temperature. New experiments performed with a Walker-type multi-anvil press on the Apollo 14 black glass were able to elucidate the separate effects of pressure and temperature. Pressure was found to have a very weak negative effect on D(Mo) over the pressure range 2.5-11.5 GPa, whereas temperature had a much stronger negative effect with D(Mo) decreasing from 97 at 1435 oC to 24 at 2020 oC. These negative pressure and temperature effects were also seen in the peridotite data set, but the partition coefficients were still well above the values required for equilibrium core formation in a magma ocean. Therefore we parameterized the peridotite data at ΔIW = -2.2 and determined a set of pressure and temperature solutions that would reproduce the observed molybdenum mantle depletions. Our solutions are consistent with equilibrium core formation in a magma ocean with temperatures >2000 K and pressures >30 GPa. |
Melting of Fe-Si alloys at high pressures: Comparison of different experimental methods |
| Andrew Campbell University of Maryland ajc@umd.edu Noah Miller, Christopher Seagle (University of Chicago), Vitali Prakapenka (University of Chicago) |
| Facility: APS-GSECARS Format: Poster |
| Silicon is a leading candidate among the possible light elements alloying with Fe in the Earthâ??s core, because of its observed depletion in the mantle and its ability to enter a metallic phase under suitably reducing conditions. Therefore, it is important to understand the melting behavior and other phase relations in Fe-Si alloys, to better evaluate siliconâ??s potential role in the core. We have determined the melting point of Fe-9%Si and Fe-16%Si at high pressures using two different diamond anvil cell methods. In one, the temperature distribution is measured during laser heating, and discontinuities in the temperature vs. emissivity trend across the laser heated spot are used to identify the melting point. The other method is to use synchrotron X-ray diffraction to monitor phase changes, including melting, in the laser heated diamond cell. The temperature vs. emissivity method defines transition temperatures with greater precision, but X-ray diffraction provides more information on the sample, including its crystal structure. The results from the two experimental methods are consistent with one another, and indicate only a small (~100 K) melting point depression of these Fe-Si alloys relative to pure Fe. If this persists to the higher pressures present in the core, then a higher core temperature is required to maintain a liquid Si-rich outer core, compared to the greater melting point depressions measured previously in Fe-S and Fe-O at high pressures. |
Diffusion of trivalent cations in MgO: Implications for diffusion in Earth?s lower mantle |
| Katherine L Crispin Case Western Reserve University katherine.crispin@case.edu James A Van Orman |
| Facility: Other Format: Poster |
| Diffusion in periclase, the second most abundant mineral in Earth?s lower mantle, is key to understanding chemical exchange mechanisms and diffusive length scales at the core-mantle boundary. Diffusion of trivalent cations is a complex process in which the impurity cations tend to bind to oppositely charged cation vacancies to form pairs, which are extremely mobile; the continual presence of a vacancy adjacent to the trivalent impurity allows it to move through the lattice much more rapidly than it would in the absence of binding. Experiments were performed on Ga, Sc, and Cr in periclase to determine rates of diffusion and the energy of binding between the trivalent cation and vacancy, at 1 atm and 2 GPa and temperatures between 1468K and 2273K. Theoretical diffusion profiles were calculated numerically, and were fit to the experimental profiles through chi-square minimization, in order to extract the binding energy and impurity-vacancy pair diffusivity. Although there is no clear trend linking diffusivity to ionic radius, Cr diffuses much more slowly than Ga despite its nearly identical ionic radius. This may be accounted for by the crystal field effect, which is controlled by d-orbital electron configuration. |
Calculating Materials Properties at High Pressures and Temperatures in VLab |
| Cesar R.S. da Silva University of Minnesota cesarrssilva@gmail.com Pedro R.C. da Silveira |
| Facility: None Format: Poster |
| VLab is a cyberinfrastructure (CI), designed to enable execution of very complex parameter sampling workflows. The calculation of thermal properties of materials at high pressures and temperatures, geo-dynamics, ocean dynamics, and meteorology are outstanding examples of target fields. VLab is composed by a Web-based portal, accessible from a web browser, and a supporting service oriented architecture (SOA). It allows for distributed high performance computing of workflows composed by hundreds or even thousands of tasks, as well as collaborative visualization, data analysis and user monitoring of all tasks in a consolidated user interface. Currently, its flagship application is the calculation of high P,T properties of materials. VLab web based interface is accessible from any computer or mobile device connected to the internet which, combined with the consolidation of analysis tools, makes it a highly empowering tool even for simple calculations, fulfilling the common requirements for a science gateway. |
VLab: A Cyberinfrastructure for Parameter Sampling Computations Suited for Materials Science Calculations |
| Pedro R.C. da Silveira University of Minnesota pedros@msi.umn.edu Cesar R.S. da SIlva |
| Facility: None Format: Poster |
| We show an overall view of the VLab cyberinfrastructure (CI), a system aimed to handle execution of extensive parameter sweeping workflows composed by concurrent heavy calculations, with consolidated analysis tools. The multiplicity of tasks coming from parameter sampling calculations can comprise hundreds or even thousands of tasks. Although the CI is general, the calculation of thermal properties of materials at high pressures and temperatures is our primary motivation. We review the algorithms of physical importance, services and metadata requirements. The CI is composed by a service oriented architecture (SOA), and a portal that handles the user interface. The SOA is implemented as a collection of web-services providing access to distributed computing resources, controlling workflow execution, monitoring services, and providing data analyses tools, visualization services, data bases, and authentication services. We also describe the metadata metaphor, which can be used for a variety of other parameter sampling calculations. We also show how analysis tools, not originally developed for VLab are integrated in the SOA. |
Measurements of low-temperature plasticity in dry olivine using the D-DIA |
| Nathaniel A Dixon Massachusetts Institute of Technology dixonn@mit.edu William B. Durham David L. Kohlstedt (University of Minnesota, Twin Cities) Shenghua Mei (University of Minnesota, Twin Cities) |
| Facility: NSLS-X17B2 (MAC) Format: Poster |
| Important unresolved issues in geodynamics demand a better understanding of the rheological strength of lithosphere, such as its role at convergent plate margins and the relative strength of crust and lithospheric mantle. With the development of a new mullite/pyrophyllite hybrid sample cell, the D-DIA apparatus has become a much more practical tool for testing the strength of mantle materials under lithospheric conditions. The mullite component of the cell has allowed for improved control of sample water content, while pyrophyllite serves as an excellent gasket material, greatly reducing the occurrence of equipment failures at high pressure. In experiments performed at beam line X17B2 at NSLS, polycrystalline samples of San Carlos olivine + 5% enstatite were deformed in triaxial compression at temperatures from 673 to 1073 K, pressures (mean stress) from 4 to 10 GPa and fixed strain rates near 3x10-5 s-1. The state of stress was calculated from changes in lattice spacing measured by x-ray diffraction in energy dispersive mode; plastic strain was recorded directly from x-radiographs, where the components of the sample assembly can clearly be seen during deformation. Measurements were taken periodically during each deformation step. We found that the flow strength of olivine increased from 2 to and 4 GPa as temperature decreased from 1073 to 673 K. These strengths are roughly consistent with those determined by Evans and Goetze, based on microindendation experiments, and considerably higher than values measured by Raterron et al. in stress relaxation tests. |
Olivine-ringwoodite transformation kinetics suggest that slabs containing 30 wt-ppm H2O are inconsistent with a metastable wedge. |
| Wyatt L Du Frane Arizona State University wd@asu.edu Thomas Sharp Kurt Leinenweber |
| Facility: Other Format: Poster |
| Hydrogen increases the growth rates of the metastable olivine to ringwoodite transformation. These ringwoodite growth rates determine the likelihood of a metastable olivine wedge persisting into the Earth?s mantle transition zone (410 to 660 km depth) in subduction zones. Transformational faulting of metastable olivine has been proposed as a triggering mechanism for deep earthquakes, and seismological evidence for metastable olivine coincides with the observed locations of deep earthquake hypocenters in subducted slabs [Kaneshima, et al., 2007; Iidaka and Suetsuga, 1992]. However it is believed that downwelling slabs are hydrated by the breakdown of serpentine [Peacock, 2001], previous results have indicated that olivine containing as little as 289 wt-ppm D2O (an H2O proxy) will transform too quickly for a metastable wedge of olivine to survive into the Earth?s transition zone [Diedrich, et al., 2007]. In this study we investigate olivine-ringwoodite transformation kinetics using olivine hydrated with 30 wt-ppm H2O. At 18 GPa and 1100 ◦C, olivine with 30 wt-ppm H2O transforms quickly, with a ringwoodite growth rate of 1.6 x 10-7 m/s, which is nearly identical to growth rates for olivine with 289 wt-ppm D2O at the same P and T. These growth rates are very rapid in comparison to those of nominally anhydrous olivine, 3.7 x 10-9 m/s at 18 GPa and 1100 ◦C, measured using the same experimental setup [Diedrich, et al., 2007]. The activation enthalpy for ringwoodite growth in olivine with 30 wt-ppm H2O (157 +/- 11 kJ/mol) is comparable to the 289 wt-ppm D2O samples (186 kJ/mol). Based on the thermo-kinetic models in Diedrich, et al. [2007], 30 wt-ppm H2O in olivine within old, cold, and fast subducting slabs would eliminate the metastable wedge of olivine. Conversely, these results imply that slabs exhibiting seismological evidence of a metastable olivine wedge, such as the subducted Mariana slab [Kaneshima, et al., 2007] and the subducted Pacific slab [Iidaka and Suetsuga, 1992], have less than 30 wt-ppm wt H2O at transition zone depths. These measurements imply that the presence or absence of a metastable olivine wedge determines rather subducting lithosphere in the Earth?s transition zone is anhydrous or hydrous. |
Magnetic Transition and Sound Velocities of Fe3C at High Pressure |
| Lili Gao Department of Geology, University of Illinois at Urbana-Champaign liligao2@uiuc.edu Bin Chen, Jingyun Wang, Fang Huang, Craig Lundstrom, Jay Bass, Jie Li (University of Illinois at Urbana-Champaign) Esen E. Alp, Jiyong Zhao, Wolfgang Sturhahn, Stanislav Sinogeikin (Advanced Phonon Source (APS), Argonne National Laboratory) Michael Lerche ( Advanced Phonon Source (APS), Argonne National Laboratory & Carnegie Institution of Washington) Yang Ding (Carnegie Institution of Washington) Henry P. Scott (Department of Physics and Astronomy, Indiana University South Bend) |
| Facility: Other Format: Poster |
| We have carried out nuclear resonant scattering measurements on 57Fe-enriched Fe3C between 1 bar and 50 GPa at 300 K. Synchrotron Mössbauer spectra reveal a pressure-induced magnetic transition in Fe3C between 4.3 and 6.5 GPa. On the basis of our nuclear resonant inelastic X-ray scattering spectra and existing equation-of-state data, we have derived the compressional wave velocity VP (ρ)(km/s) = -3.99 + 1.29ρ (density, g/cm3) and shear wave velocity VS(ρ) = 1.45 + 0.24ρ for the high-pressure nonmagnetic phase. The addition of carbon to iron-nickel alloy brings density, VP and VS closer to seismic observations, supporting carbon as a principal light element in the Earth's inner core. |
The 4-Laue Monochromator At X17B3 Beamline of National Synchrotron Light Source |
| Quanzhong Guo Stony Brook University qguo@bnl.gov Zhong Zhong, NSLS of Brookhaven National Laboratory Jingzhu Hu, Stony Brook University |
| Facility: NSLS-X17B3 (DAC) Format: Poster |
| On the basis of theory and practice experiments from the two asymmetric Laue crystals monochromator system at the X17B1 and X17C beam lines, we designed the 4-Laue monochromator at X17B3. By using 4 of Laue crystals to keep the mono beam and white beam are at the same position and then let users easily switching experiments between angle dispersive X-ray diffraction (ADXD) and energy dispersive X-ray diffraction (EDXD) without moving the samples. The prototype sagittal focusing monochromator using four asymmetric Laue crystals with 30 keV X-rays, has been constructed and tested successfully at the X17B3. The x-ray flux, from the 4-Laue monochromator with the above prototype setting, is about one tenth of the magnitude of the two-crystal Laue monochromators, as expected. The optimized crystal thickness experiment of Si was performed to increase the x-ray flux. Recently, from the studies on Si crystal?s surface, we have gained a much better understanding of the coupling problems between crystals. The flux of 4-Laue monochromator using a pair of crystals instead of the single one at around 30KeV energy should be similar as the present two-Laue system. With the energy-tunable 4-Laue mono beam combined the EDXD technique at X17B3 will be the great potential application for minerals and material scientist. |
Serpentine rheology and dehydration at high pressure, implications for intermediate depth seismicity |
| Nadege Hilairet University of Chicago, GSE-CARS hilairet@cars.uchicago.edu Bruno Reynard(1), Isabelle Daniel(1), Yanbin Wang(2) (1) Laboratoire des Sciences de la Terre, CNRS UMR 5570, Ecole normale superieure de Lyon, Universite Claude Bernard Lyon 1 (2) Center for Advanced Radiation Sources, The university of Chicago |
| Facility: APS-GSECARS Format: Poster |
| Serpentinites have a low viscosity compared to other mantle and slab materials within subduction zones. Their rheology is likely to govern stress building-up and relaxation at the slab surface during interseismic time. Serpentine dehydration is also believed to play a major role in intermediate-depth seismicity, and several mechanisms have been proposed such as dehydration embrittlement and shear heating. Antigorite deformation experiments were carried out both within its stability field, and during dehydration, over a pressure temperature (P-T) range of 1 - 4 GPa and 200-700 /deg C, at strain rates between ~10-4 and 10-6 s-1, in a D-DIA apparatus at GSE-CARS (Advanced Photo Source). Strain rates and stresses were obtained respectively from in-situ monitoring the sample length with X-ray radiographs, and azimuthal dependence of d-spacings on monochromatic X-Ray diffraction patterns. The results from these experiments will be presented. Most importantly, at the lowest strain rate investigated and nominal T within the antigorite stability field we observed a localization accompanied by a moderate increase in strain rate. The implications for the role of serpentinites in intermediate-depth seismicity within subduction zones will be discussed. |
Potassium's Potential in Earth's Core |
| Sabrina ARA Huggins The Ohio State University huggins.43@osu.edu Sabrina Huggins, Wendy Panero, Daniel Reaman, Jason Kabbes |
| Facility: NSLS-X17C (DAC) Format: Poster |
| Long-lived radionuclides such as potassium, rubidium, uranium, and thorium are sources of heat generation in the interior of the Earth. Yet the budget of alkali metals in the bulk silicate earth falls below the expected values when compared to chondritic values and accounting for volatility. This discrepancy lends itself to the possibility that potassium could be located in the Earth?s core, requiring that it be able to form solutions with iron. At high-pressures, potassium undergoes an electronic transitions, which makes it behave like a transition metal, and potentially allowing it to form iron alloys at core pressures. However, previous high-pressure diamond anvil cell studies of potassium solubility in iron show discrepant results as to the possible concentration of potassium in the core. One explanation for the difference in the overall incorporation of potassium into iron is the amount of oxidation that iron undergoes as an experiment is prepared for analysis through contact with air. Results from samples could be compromised by the oxidation of iron in either the powdered form or as a foil as a result of the potassium interacting with the surface iron oxide. We present results on experiments in which we measure the potassium incorporation in iron via lattice expansion for experiments when iron foil is loaded in air compared to iron foil loaded in a nitrogen environment after cleaning surface oxidation with a 6 molar solution of HCl. We observe no significant difference in the volume expansion of iron between the two sets of experiments, with volume expansions of 1-2%, consistent with ~500 ppm K in iron at pressures of 30-90 GPa. |
The behavior of iron in (Mg,Fe)SiO3 post-perovskite under megabar pressures |
| Jennifer M Jackson California Institute of Technology jackson@gps.caltech.edu Wolfgang Sturhahn (Argonne National Laboratory), Oliver Tschauner (University of Nevada), Michael Lerche (HPSynC, Carnegie Institution of Washington), and Yingwei Fei (Carnegie Institution of Washington) |
| Facility: APS-HPCAT Format: Poster |
| The bottom few hundred kilometers of Earth's mantle, termed the D" layer, represents one of the most extreme compositional and thermal boundary layers within our planet, where the solid silicate and (Mg,Fe)O dominant mantle is in contact with with the iron-dominant outer core. Knowledge of the behavior of iron in this material, which in turn may influence elastic and transport properties, provides important constraints on our understanding of this boundary layer. (Mg,Fe)SiO3 has been suggested to crystallize in the post-perovskite structure under the pressures and temperatures of Earth's D" layer, and is therefore the focus of many current experimental and theoretical investigations. We have measured the hyperfine fields of iron in (Mg,57Fe)SiO3 post-perovskite at megabar pressures using synchrotron Mössbauer spectroscopy at Sector 3 ID-B of the Advanced Photon Source at Argonne National Laboratory. We compressed orthoenstatite-structured (Mg,57Fe)SiO3 in diamond anvil cells to over one megabar and then used a CO2 laser to synthesize the material off-line into a post-perovskite structure. Evaluation of the synchrotron Mössbauer data provides the electric field gradient (quadrupole splitting) and s-electron density (isomer shift) of the iron sites, which in turn provides constraints on the valence and spin state of iron. |
Effect of water on the density of ultramafic silicate melts at high pressure |
| Zhicheng Jing Department of Geology and Geophysics, Yale University zhicheng.jing@yale.edu Shun-ichiro Karato |
| Facility: None Format: Poster |
| Density of silicate melts is important to understand the geochemical evolution of the Earth, since the density contrast between melts and surrounding solids determines the direction of the melt migration, and hence the fate of incompatible elements. Water may have a relatively large effect on melt density compared to other oxide components in the melt as shown by previous studies (Matsukage et al., 2005; Sakamaki et al., 2006; Agee, 2008). However, experimental data are still very limited to fully constrain the effect of water on melt density. In this study, we perform sink/float experiments using a Kawai-type multianvil apparatus to determine the density of hydrous ultramafic silicate melts at high pressure. In this method, density markers are loaded into sample capsules. The sample is then completely melted under high-pressure and high-temperature conditions. After quenching the density of the melt can be bracketed by the sinking or floating of the density markers in each experiment. The experimental setup is similar to Matsukage et al. (2005). Diamonds are used as density markers. We have studied 2 hydrous melt compositions, s6_3 with 3 wt% water, s6_7 with 7 wt% water by adding or subtracting water from the melt composition s6a with 5 wt% water in Matsukage et al. (2005). Another dry composition s7 which is the dry part of s7a in Matsukage et al. (2005) is also studied. Experimental conditions are from 8 to14 GPa and from 2173 to 2373 K. The density of these melts will be analyzed by fitting a normalized Birch-Murnaghan equation of state (Jing & Karato, 2008, accepted). Given the effect of water on room-pressure density and room-pressure bulk modulus from previous calibrations (e.g., Lange, 1997), the effect of water on the pressure derivative of bulk modulus of the melts will be constrained. We will also discuss the conditions under which the density crossover between hydrous melts and the surrounding solids at 410 km could occur. |
THE PHASE DIAGRAM AND THERMOELASTIC BEHAVIOR OF SILVER IODIDE |
| Abby Kavner UCLA akavner@igpp.ucla.edu K. Havens M. Armentrout R. Kundargi M. Kunz, ALS S. M. Clark, ALS |
| Facility: ALS Format: Poster |
| The silver halides are industrially important ionic conductors and model systems for mineral physics behavior. Their structural phase transformations and thermoelastic behavior provide ground truth for theoretical models predicting the behavior of ionic materials at high pressure conditions of the Earth?s deep interior. We studied the high-pressure, high-temperature phase stability and thermoelastic behavior of AgI using synchrotron X-ray diffraction in conjunction with in situ laser heating at beamline 12.2.2 at the Advanced Light Source in Berkeley, CA. We document the presence a new high temperature-high pressure stable phase of AgI, with a structure that is similar to the thallium iodide orthorhombic structure. The P(V) equation of state of this new phase was measured using energy-dispersive diffraction at NSLS beamline X17C. In this poster, we present a newly determined high pressure/high temperature for AgI, and thermoelastic behavior of the high pressure phases. We show how this new data set helps constrain systematics of physical and chemical properties across the the halide family. |
Aluminum and silicon coordination changes in high pressure sodium aluminosilicate glasses: NMR results |
| Kimberly Kelsey Stanford University kkelsey@stanford.edu Jonathan F. Stebbins, Stanford University Jed L. Mosenfelder, California Institute of Technology Paul D. Asimow, California Institute of Technology |
| Facility: None Format: Poster |
| Understanding the structure of high pressure aluminosilicate glasses can better constrain the macroscopic properties and igneous processes in the upper mantle. As melts densify, bond angles and distances change and the average coordination number (CN) for some of cations increases. Both Al and Si can increase CN, however in aluminosilicate glasses, it appears Al changes coordination more readily than Si . In previously observed glasses containing [5,6]Al, [5,6]Si has been undetectable (0.5 ? 2 % detection limits). This study uses nuclear magnetic resonance (NMR) spectroscopy to investigate how the presence of small to moderate amounts of aluminum affects silicon coordination changes. 29Si MAS NMR spectra of 6GPa Na2Si3O7 glasses with no Al show the presence of 2 % [5]Si and 2 % [6]Si. A glass with 0.6 wt % Al2O3 and the same nominal NBO/T has very similar Si coordinations, even though the Al has an average CN of 5.49, the most rapid increase in Al coordination with pressure yet observed in an aluminosilicate. Thus, although Al increases CN more readily than does Si, the addition of Al does not inhibit the formation of high coordination Si. Similarly, Na2Si4O9 glasses with 0.3 wt % Al2O3 also have 3 % [5]Si and 3 % [6]Si and an average Al CN of 5.19. When the aluminum concentration increases, there is a gradual decrease in both the average Al CN and the average Si CN, however, the overall tetrahedral (T) CN increases. There is a similar decrease in average Al CN and increase in T CN with increasing aluminum concentrations in ambient pressure glasses. We present the first direct evidence for both [5,6]Al and [5,6]Si present in high pressure sodium aluminosilicate glasses with up to 15 wt % aluminum. |
Topological mechanisms of decompression in silicate liquids from 5-0 GPa: their critical, yet often overlooked, role in promoting partial melting of the upper mantle |
| Rebecca Lange Dept. of Geological Sciences, University of Michigan, Ann Arbor, MI 48109-1005 becky@umich.edu |
| Facility: None Format: Poster |
| The compressibility of silicate liquids is much larger than that of corresponding crystals at low pressures (e.g., 0-5 GPa), with the difference decreasing with increasing pressure. This enhanced compressibility of liquids at low pressures has consequences for the density difference between partial melts and the crystalline upper mantle, which affects the amount of melt generated during decompression and increases the buoyancy drive of the resulting partial melts. Despite the importance of the enhanced compressibility of liquids relative to solids at low pressures (especially for the extraction of oceanic and continental crust out of the mantle), its cause has often been overlooked. Instead most of the focus on understanding the structural mechanisms of liquid compressibility has been limited to Al3+ and Si4+ coordination change. Here, a discussion of the importance of topological mechanisms of compression (and expansion) in liquids at low pressure is presented. The principal mechanisms of compression for minerals (also available to liquids) involve changes in either bond lengths or T-O-T bond angles. Minerals may also undergo an abrupt phase transition, in which there is either a change in cation coordination (e.g., coesite to stishovite) or topology (quartz to coesite), both of which involve bond breaking and can induce a large change in density. In contrast, liquids may undergo continuous and gradual changes in cation coordination and/or topology, both of which require that bonds be broken and reformed and thus reflect the dynamic character of liquids relative to solids. The magnitude of these topological mechanisms of compression (and expansion) can be seen by comparing the compressibility of liquid KAlSi3O8 to that of sanidine as a function of pressure. At one bar, the compressibility of liquid KAlSi3O8 is 264% larger than that of its crystalline equivalent; this difference diminishes to a 19% difference by 6.5 GPa. There is little evidence for coordination change of either Al3+ or Si4+ in KAlSi3O8 liquid at low pressure, so that the enhanced liquid compressibility clearly involves topological mechanisms (e.g., changing from a tridymite to a feldspar topology) rather than one based on Si/Al coordination change. This mechanism of compression rapidly increases with decreasing pressure and facilitates the large density difference between liquid and crystal at one bar. Another example of the importance of topological mechanisms of compression (and expansion) in liquids is seen with the volume of fusion of diopside (~17%) at one bar. The 17% increase in volume cannot be explained by a change in Si4+ coordination number or by mechanisms of expansion available to crystalline diopside. In fact, crystalline diopside would have to be heated by more than 2000 degrees above the one-bar melting temperature in order to increase its volume by 17%. Thus, the best explanation for the large volume of fusion is a change in the average topology of CaMgSi2O6 liquid (e.g., the formation of Si3O9 rings) relative to crystalline diopside. Clear evidence for the role of topological mechanisms of compression for CaMgSi2O6 liquid is found by comparing its compressibility curve with calculations of its average Si4+ coordination number with depth. This permits a quantitative assessment of how the absence of topological mechanisms of compressibility would affect the fusion curve of diopside, namely to make it more refractory at one bar by ~200 degrees. Thus, topological mechanisms of compression (and expansion) in magmatic liquids play a profound role in the efficient extraction of oceanic and continental crust out of the uppermost mantle. The unique role of FeO, Al2O3, TiO2 and dissolved water in contributing to the topological mechanisms of silicate melts at low pressure will also be discussed. |
Monochromatic single crystal diffraction at high pressure |
| Barbara Lavina GSECARS, University of Chicago, Chicago, IL lavina@cars.uchicago.edu Przemyslaw Dera, Lauren Borkowski (High Pressure Science and Engineering center, UNLV, Las Vegas, NV), Vitali Prakapenka |
| Facility: APS-GSECARS Format: Poster |
| Monochromatic single crystal diffraction has been recently developed for the investigation of crystal structure at high pressure generated with the DAC. Two-dimensional patterns are collected in omega-scan mode, this allows one to obtain a reasonable 3-dimensional coverage in the reciprocal space. We were able to determine lattice parameters, and consequently compression curves, with high accuracy up to 60 GPa. We will also show some examples of phase transition characterizations, obtained either in cold compression or after laser heating. We focused our investigations on structures of high significance for the earth?s interior, such as phosphates of transition metals and Mg-Al spinels. Phase transitions from single crystal to single crystal, from single crystal to powder, from single crystal to polysynthetic twin were obtained after cold compression and with the aid of laser heating. |
Raman spectroscopic studies of ammonia borane at high pressure |
| Yu Lin Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305 lyforest@stanford.edu Wendy L. Mao, JiuHua Chen(Stony Brook University) |
| Facility: APS-HPCAT Format: Poster |
| Ammonia borane, NH3BH3, has attracted significant interest as a promising hydrogen storage candidate. The effect of pressure on the bonding in NH3BH3 was investigated using Raman spectroscopy up to 22.30 GPa in a diamond anvil cell. Vibrational modes of the NH3 proton donor group exhibit negative pressure dependence, which is consistent with the behavior of conventional hydrogen bonds, while the vibrational modes of the BH3 proton acceptor group show positive pressure dependence. A number of phase transitions occur in over the pressure range studied. The observed behavior of these stretching modes supports the presence of dihydrogen bonding under high pressure and provides guidance for understanding and developing improved hydrogen storage materials. |
High-temperature-pressure Study of Zirconium-based Carbides |
| Zhijun Lin LANSCE-LC, Los Alamos National Laboratory, NM 87545, USA zjlin6@gmail.com Zhijun Lin 1,*, Jianzhong Zhang 1, Yuejian Wang 1, Linfeng He 2, Yanchun Zhou 2, Liping Wang 3, and Yusheng Zhao 1,* 1) LANSCE-LC, Los Alamos National Laboratory, NM 87545, USA 2) Shenyang National Laboratory for Materials Science, Institute of Metal Research, CAS, Shenyang 110016, China 3) Mineral Physics Institute and Department of Geosciences, Stony Brook University, Stony Brook, New York 11794-2100, USA *Corresponding authors: zlin@lanl.gov (Z.J. Lin), yzhao@lanl.gov (Y.S. Zhao) |
| Facility: NSLS-X17B2 (MAC) Format: Poster |
| Zirconium-based carbides play an important role in ultrahigh-temperature applications due to the fact that they exhibit excellent mechanical and chemical properties at elevated temperatures. Synchrotron x-ray diffraction experiments on zirconium-based carbides (Zr2[Al,Si]4C5, and ZrC) were conducted using a cubic anvil apparatus at beamline X17B2 of the National Synchrotron Light Source, Brookhaven National Laboratory. We used a cubic mixture of amorphous boron and epoxy resin as pressure-transmitting medium, and amorphous carbon as furnace material. The two samples were studied simultaneously in a single experiment; they were packed into a cylindrical container of boron nitride (BN), separated by a layer of NaCl powders, which also served as internal pressure standard. The pressures were determined using the Decker equation of state for NaCl and temperatures were measured by a W/Re25%-W/Re3% thermocouple. Results on the equation of state and strength of both compounds will be presented. The difference between these two carbides is interpreted from their crystal structures and bonding properties. |
Stability of magnesite in the deep mantle |
| Konstantin D Litasov Geophysical Laboratory, Carnegie Institution of Washington klitasov@ciw.edu Yingwei Fei, Alexander Goncharov, Angele Ricolleau, Yue Meng, Maddury Somayazulu, Russell Hemley |
| Facility: APS-HPCAT Format: Poster |
| Thermal modeling of subducting slabs indicate that significant amount of carbonates can be transported to the deep mantle. After decomposition of dolomite at about 4.5 GPa and 1273 K, magnesite is a major carbonate phase, which store oxidized carbon in mantle-related assemblages of peridotite and eclogite. Here we report the results on magnesite stability in a symplified carbonated peridotite and eclogite at pressures 10-32 GPa and preliminary results on magnesite + SiO2 = MgSiO3 + CO2 (fluid/solid) reaction at 20-70 GPa. We performed multianvil experiments at Tohoku University and SPring-8 synchrotron facility and laser-heating diamond anvil cell experiments (DAC) at Geophysical Laboratory (Raman) and HPCAT 16ID-B beam line of APS (X-ray diffraction). In multianvil study of carbonated peridotite and basalt we observed that (a) solidi of carbonated peridotite and basalt have much gentler slopes at 10-32 GPa than at lower pressures; (b) partial melts of low degree melting have magnesiocarbonatite and calciocarbonatite composition in peridotite and basalt, respectively, whereas higher degree partial melting produce kimberlitic silicate melt; (c) stishovite may not coexist with carbonatite melt because of high mutual reactivity. In situ X-ray diffraction study using multianvil apparatus show fast transformation of magnesite + stishovite to Mg-perovskite + CO2 at 25.4 GPa and 2073 K. Preliminary DAC results show that formation of Mg-perovskite occurs at higher temperature than observed by Takafuji et al. (2006) for this reaction at approximately 2100-2400 K in the pressure range of 20-70 GPa. However we could not identify solid CO2 by X-ray diffraction and Raman to date. |
In situ Ultrasonic observations of elasticity changes across the phase transformation in Fe2SiO4 at 1173 K |
| Qiong Liu Mineral Physics Institute, Stony Brook University qioliu@notes.cc.sunysb.edu Wei Liu, Matthew Whitaker, Liping Wang, and Baosheng Li |
| Facility: NSLS-X17B2 (MAC) Format: Poster |
| Olivine to spinel transformation in (Mg,Fe)2SiO4 is known to be responsible for the observed seismic discontinuities and play a major role in the behavior of subducting slabs. It is therefore important to determine the transformation pressure, kinetics, density and elasticity variations associated with this transition in order to understand the structure and dynamics of the upper mantle. In this study, compressional and shear wave velocities of spinel to olivine and the reverse transformation in Fe2SiO4 were investigated in situ using combined synchrotron X-ray diffraction, X-ray imaging, and ultrasonic interferometry at 1173 K up to 5.5 GPa. The experiment was conducted in a DIA-type cubic anvil apparatus (SAM85) installed at beamline X17B2, NSLS in Brookhaven National Laboratory. Pre-compressed boron epoxy cube was used as the pressure medium. The sample was surrounded by a mixture of NaCl and BN inside a BN sleeve to provide a pseudo-hydrostatic condition for the sample. A 10o Y-cut LiNbO3 dual-mode transducer was used for simultaneous generation of P and S waves. Double polished alumina rod was used as buffer rod. X-ray diffraction data for both the sample and NaCl were collected in energy dispersive mode for phase identification and sample pressure calculation. X-ray radiographic imaging was used to derive the sample length. The onset of the transformation from 4.2 to 4.8 GPa at 1173 K was consistent from the X-ray diffraction pattern, the amplitude of the ultrasonic signals, and the calculated velocities. The velocity jumps in P and S waves across the phase transitions between 4.2 and 4.8 GPa are derived directly from the measured velocities. |
Olivine Instability: An Experimental View of Mechanism of Deep Earthquakes |
| Hongbo Long Stony Brook University hlong@ic.sunysb.edu Hongbo Long, Donald J. Weidner, Li Li, Jiuhua Chen, Liping Wang |
| Facility: NSLS-X17B2 (MAC) Format: Poster |
| Experimental study regarding to the effects of annealing process, grain size and water existence on deformation of polycrystalline San Carlos olivine has been performed on a D-DIA facility at X17B2, NSLS. The total macroscopic strain is derived from the direct measurements of the images taken by X-ray radiograph technique. Differential stress is measured at constant strain rate (~10-5-10-7s-1) and at different temperatures with synchrotron x-ray. Olivine in the annealed/unannealed system shows similar properties during the deformation. However, the annealing process can shift the transition temperature between regimes of temperature insensitive and sensitive to the high value side as much as 370¡ãC. Grain size affects the rheological properties of olivine in the low temperature dislocation regime. Existence of water obviously decreases the transition temperature of the boundary between the regimes of low temperature plasticity and paw-law creep. The instability of olivine could be the mechanism for the deep-focus earthquake happened in the subduction zone slab. |
Effects of hydration on the elasticity of olivine to 14 GPa |
| Zhu Mao Princeton University zhumao@Princeton.EDU Steven D. Jacobsen(Northwestern University), Fuming Jiang, Joseph R. Smyth (University of Colorado at Boulder), Christopher M. Holl (Northwestern University), Thomas S. Duffy |
| Facility: None Format: Poster |
| Measurements of the elasticity of hydrous olivine polymorphs are essential to interpret the seismic observations and constrain the water content in the earth's mantle. To explore the effect of pressure on the elasticity of hydrous olivine, we conducted Brillouin scattering measurements to 14 GPa on single-crystal samples previously studied at 1 bar by Jacobsen et al., (2008). At ambient conditions, the aggregate bulk and shear moduli of olivine with 0.9 wt% H2O are offset to lower values by 2.2-2.4% compared with anhydrous olivine (Zha et al., 1996; Jacobsen et al., 2008). With compression, aggregate bulk and shear moduli of hydrous olivine increase faster than those of the corresponding anhydrous phase. Compared with anhydrous olivine, 0.9 wt% H2O increases the pressure derivatives of the bulk modulus of olivine from 4.2 (2) (Zha et al., 1996) to 4.5(1), and of the shear modulus from 1.4(1) to 1.8(1). Using our measured elasticity of hydrous olivine, we calculate the compressional and shear wave velocities of olivine 0.9 wt% H2O as a function of depth along 1400oC adiabat. We assume the temperature derivatives of the bulk and shear moduli of hydrous olivine are the same as those of anhydrous phase. Compressional and shear velocities of olivine with 0.89 wt% H2O are slower than anhydrous olivine at 0 km but become faster than anhydrous phase beyond 150 km and 100 km respectively. Effect of anelasticity from a preliminary model (Karato 2006) accounting for the effect of H2O was incorporated into further calculations. This model indicates that the effect of anelasticity on the shear velocity of olivine with 0.89 wt% H2O may offset the increase in the anharmonic components of hydrous olivine. The net effect would be that seismic velocities in the hydrous olivine would be comparable to in dry olivine at 410 km. |
Experimental investigation of the hydrous characteristics of pressure media |
| Shenghua Mei University of Minnesota meixx002@umn.edu Ayako Suzuki, Shenghua Mei, and David L. Kohlstedt |
| Facility: NSLS-U2A (DAC) Format: Poster |
| The pressure medium plays an important role in high-pressure studies. Materials such as pyrophyllite, boron epoxy resin, and mullite are commonly used as pressure media for experiments in a D-DIA press because these materials have either the strength necessary to achieve good pressure efficiency or sufficient ductility to form competent gaskets bounding the six anvils used in the D-DIA press. However, some of these materials might release water at or below the experimental temperature. If water is supplied by the pressure medium, it is often problematic for interpreting the measured material properties, many of which are affected by the presence of water. As one example, the rheological properties of olivine are affected by even a trace amount of water. Therefore, the hydrous characteristic of pressure media must be well documented in order to provide both a reference for selecting a pressure medium for a specific experiment and a basis for estimating the effect of water on physical properties of the sample. Experiments have been carried out using a D-DIA off-line in our laboratory. Samples 1 mm in length x 1.1 mm in diameter were prepared from oriented San Carlos olivine single crystals, encapsulated with 0.025-mm thick Ni foil, and assembled with alumina pistons, a boron nitride sleeve, and a graphite resistance heater into a 6-mm edge length cubic pressure medium. The cell was then annealed at high temperature (1473 K) and high pressure (~6 GPa) for 6 h. After the run, the water content in the olivine sample was determined using FTIR spectroscopy. Such experiments were done with using different pressure media including pyrophyllite, boron epoxy resin, and mullite for documenting the hydrous characteristics of these commonly used media. |
Numerical Simulations of Falling Sphere Viscometry Experiments |
| Lara O'Dwyer Brown Geology, University of California Davis odwyerbrown@geology.ucdavis.edu Louise H. Kellogg Charles E. Lesher |
| Facility: None Format: Poster |
| To experimentally determine the viscosities of geologically relevant melts at high pressures the falling sphere technique based on Stokes' law is widely used. Stokes' law is valid when a rigid sphere falls slowly and steadily through a stationary and infinite homogeneous Newtonian medium. High-pressure falling sphere experiments however, usually involve dropping a dense, refractory sphere through a liquid contained by a cylindrical capsule of finite size. The walls and the ends of the capsule, as well as possible convective motion of the fluid influence the sphere velocity. We utilize GALE (Moresi et al., 2003), a finite element particle-in-cell code, to examine these factors by numerically simulating conditions similar to those of high-pressure experiments. Our modeling considers a cylinder containing a cluster of particles that represent the dense sphere in laboratory experiments surrounded by low viscosity particles representing the melt. GALE includes buoyancy forces, heat flow, and viscosity variations so our model can be used to assess the effects of the capsule's walls and ends, non-centered sphere trajectories, the presence of multiple spheres, varied cell geometries reflecting laboratory experimental innovations, and the consequences of thermal gradients on the sphere's velocity and trajectory. Comparisons between our numerical simulations and real-time falling sphere experiments involving lower viscosity molten komatiite are made to assess the validity of Stokes' law given the above mentioned experimental challenges. Our models show that the velocity profile in the cylinder is parabolic, and as the sphere falls closer to the wall its velocity decreases. In addition, preliminary results indicate that the presence of two appropriately spaced spheres does not significantly influence their respective terminal velocities. These results are encouraging as they suggest that experimental modifications to the simple falling-sphere experiment do not adversely affect the measurement of viscosity. |
High Pressure Studies of GaFeO3 |
| Moshe paz Pasternak School of Physics and Astronomy, Tel Aviv University, 69978, Tel Aviv, Israel moshepa@tau.ac.il R. Arielly, W. M. Xu, E. Greenberg, G. Kh. Rozenberg M. Hanfland,European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble, France. R. Jeanloz,Department of Geology and Geophysics, University of California, Berkeley, California 94720 R.D. Taylor,MPA-10, MS-K764, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 |
| Facility: Other Format: Poster |
| Electronic and structural properties of the high-pressure phase of the piezoelectric and ferrimagnetic GaFeO3 were documented to 100 GPa by combining the methods of high-pressure 57Fe Mössbauer spectroscopy (MS), with its hyperfine interactions used as a magnetic probe, synchrotron X-ray diffraction, and electrical resistance, R(P,T). Within the experimental error the pressure-dependence of the 57Fe hyperfine field in the 0-60 GPa range manifests to a negligible contribution of the orbital-term of the Fe3+ magnetic moment. This observation may question the presence of any orbital magnetic moment derived from a L≠0 term that has previously been invoked to explain the magnetic-electric properties of GaFeO3. A discontinuous decrease in resistance indicates that an insulating-metal transition takes place at 53-68 GPa, and the observed collapse of the 57Fe magnetic hyperfine field signals the transition of a correlated (Mott-Hubbard) to a non-correlated state at the same pressures. Within the paramagnetic pressure regime the Néel temperature increases with pressure, from 200 K at P = 0 to 300 K at 33 GPa. The isomer shift gradually decreases with pressure, showing a sudden drop above 60 GPa. The pressure-induced electronic-magnetic transition is similar to that found in Fe2O3. The equation of state, measured to 30 GPa by x-ray diffraction, yields a zero-pressure bulk-modulus of K0=254(4) GPa, close to that of Fe2O3 |
Phase transition in USiO4 coffinite to reidite structure between 15 and 17 GPa. |
| Daniel M Reaman The Ohio State University reaman.5@geology.ohio-state.edu Wendy Panero Veronique Pointeau (University of Michigan) Maik Lang (University of Michigan) Fuxiang Zhang (University of Michigan) Rod Ewing (University of Michigan) Christophe Poinssot (CEA Saclay) |
| Facility: NSLS-U2A (DAC) Format: Poster |
| Zircon (ZrSiO4) is present in a wide variety of igneous, metamorphic and sedimentary settings, and is stable to pressures of 19.7 GPa [van Westrenen et al, 2004] before undergoing a phase transition to the reidite structure. This refractory mineral retains a variety of trace elements including uranium. To better understand the high-pressure behavior of how zircon might store uranium in the Earth's interior, we examined coffinite (USiO4 ? nH20), which is isostructural with zircon. We have measured X-ray diffraction patterns and infrared absorption spectra (FTIR) of USiO4 coffinite to 45 GPa at X17C and U2A of NSLS. Combined analysis of x-ray diffraction and infrared spectroscopy show a phase transition to the reidite structure between 15.5 and 17.2 GPa. Rietveld refinement of x-ray diffraction patterns shows the coffinite structure stable to 13.6 GPa. Between 15.5 and 17.2 GPa we observed an abrupt change in the wavenumber corresponding to the Si-O bonds (Äí= 37 cm-1), consistent with the zircon to reidite transition at 19.7 GPa. Simultaneous with the structural changes, we observe abrupt changes in the O-H frequency (Äí = -92 cm-1) and near IR electron transitions in U4+ (Äí = 83 cm-1) and U5+ (Äí = -131 cm-1). The coffinite-reidite phase change occurs at lower pressures than the zircon-reidite phase change (19.7 ? 23 GPa). Trace element substitution has also shown to play a role on the pressure required for this phase transition [van Westrenen et al, 2004]. Further study will yield a better understanding of the micro-scale mechanisms responsible for phase transitions in silicate minerals. |
Presenting Information about the Earth's Interior on Google Earth |
| Glenn A Richard Mineral Physics Institute, Stony Brook University Glenn.Richard@sunysb.edu |
| Facility: None Format: Poster |
| The Google Earth Community (GEC) attracts a large volume of visitors to their web-based Forums, including educators, students, and casual browsers. This group includes over 1 million registered members, and many times more people who visit its Forums without registering. While Google Earth itself is primarily designed to enable users to explore the surface of the Earth and the sky, the audience that the GEC attracts is generally interested in learning about multiple aspects of the Earth system, including its interior. The standard Google Earth layers and the data offered by the GEC include information about volcanoes, seismic events, tectonic plate boundaries, and other features and phenomena related to the Earth's interior, but there is very little direct information provided specifically about the Earth's mantle and core. We have initiated a thread entitled Interior of the Earth on the GEC Forums, in order to mitigate this lack of information about the great bulk of the Earth that serves as the focus of the COMPRES mission. Our thread currently includes a web page with a kmz file that can be opened in Google Earth to display its contents. While the current kmz file does not refer to specific locations on the Earth in addition to its interior, there is the potential to expand it to identify surface manifestations of deep Earth phenomena. Our GEC thread can also be enhanced to present additional fundamental content as well as links to other sources of additional information. We welcome members of the COMPRES community to offer suggestions to us or to post information directly on the GEC Forums. Please contact Glenn Richard at the COMPRES Central Office, if you would like to discuss how best to make information available through this medium. |
The COMPRES/GSECARS Gas Loading System at the APS |
| Mark Rivers University of Chicago rivers@cars.uchicago.edu Vitali B. Prakapenka(1), Atsushi Kubo(1), Clayton Pullins(1), Christopher M. Holl(2), and Steven D. Jacobsen(2) 1 Center for Advanced Radiation Sources, University of Chicago, Chicago, IL, USA 2 Department of Earth and Planetary Sciences, Northwestern University, Evanston, IL, USA |
| Facility: APS-GSECARS Format: Poster |
| Experiments in the diamond anvil cell are frequently performed at the APS, in particular at GSECARS (sector 13), HP-CAT (sector 16), and at XOR sectors 1 and 3. In order to have the sample in the DAC be subject to a quasi-hydrostatic pressure it is necessary to surround the sample with a pressure medium that is weak, chemically inert, optically and x-ray transparent. Helium and neon are ideal because of their low x-ray scattering cross sections and low strength, which minimizes the lattice strain in the sample. However, it is necessary to load them into the DAC at a high gas pressures. GSECARS and COMPRES have developed a high pressure gas loading system with the following features: ? Able to load many kinds of DACs. A closure mechanism (motor driven screws) closes a clamping device, which in clamps the DAC closed. ? Optical access to view the cell while loading. This allows use of an online ruby fluorescence system for directly measuring the pressure as the cell is closed. ? Easy to safely operate. Use of air-driven valves, safety interlocks, and computer control. We have now loaded more than 30 cells, with nearly 100% success rate. We have loaded two types of cells with He or Ne at pressures of about 25,000 PSI. A new cell holder is being fabricated that can accomodate additional cell designs. |
Pyrometry in the Multianvil Press: New implication for temperature measurement in large volume press experiments |
| Takeshi Sanehira Consortium for Advanced Radiation Sources (CARS), the University of Chicago sanehira@cars.uchicago.edu Yanbin Wang, Vitali Prakapenka, Mark Rivers |
| Facility: APS-GSECARS Format: Poster |
| Temperature measurement in large volume press experiments has been based on thermocouple emf, which has well known problems: unknown pressure dependence of emf, chemical reaction between thermocouple and other materials, deformation related texture development in the thermocouple wires, and so on. However, there have been few other attempts in measuring temperature in large volume press experiments using techniques other than the thermocouple. Here we report a new development using pyrometry in the multianvil press, where temperatures are derived on the basis of spectral radiometry. Several high pressure runs were conducted using the 1000 ton press with a DIA module installed at 13 ID-D GSECARS beamline at Advanced Photon Source (APS). The cubic pressure medium, 14 mm edge length, was made of soft-fired pyrophyllite with a graphite furnace. A moissanite (SiC) single crystal was built inside the pressure medium as a window for the thermal emission signal to go through. An MgO disk with 1.0 mm thickness was inserted in a gap between the top of the SiC crystal and thermocouple hot junction. The bottom of the window crystal was in direct contact to the tip of the anvil, which had a 1.5 mm diameter hole drilled all the way through the anvil axis. An optical fiber was inserted in this hole and the open end of fiber was in contact with the SiC crystal. Thermal spectral radiance from the inner cell assembly were obtained via the fiber and recorded by an Ocean Optics HP2000 spectrometer. The system response of spectrometer was calibrated by a tungsten ribbon ramp (OL550S, Optronic Laboratories, Inc.) with standard of spectral radiance. Cell assembly was compressed up to target value of 15 tons and then temperature was increased up to 1573 K. Radiation spectra were mainly obtained above 873 K and typical integration time was 1 ms. Data collection was done in the process of increase and decreased of temperature. In one in-situ experiment, pressures near the thermocouple were derived from the equations of state for gold or MgO, and the pressure values varied from ~0.1 to 1.0 GPa at various temperatures. Two different calculations were made to infer temperature based on pyrometry, one was made based on Planck radiation function and the other was made by Wien?s law. Calculated temperatures above ~1200 K were generally consistent with those obtained from the thermocouple emf within ~30 K in both calculation results. However, below 1200 K, temperatures based on Planck radiation function were way off from those by thermocouple emf due to low signal-to-noise ratio. The results of detail analyses and future improvements will be discussed. |
Stability and Elasticity of Post-Perovskite Phase from High Iron and Aluminum Garnet and Its Implications to D? layer |
| Sean R Shieh Department of Earth Sciences, University of Western Ontario sshieh@uwo.ca Thomas S. Duffy Department of Geosciences, Princeton University Atsushi Kubo, Vitali B. Prakapenka GSECARS, University of Chicago |
| Facility: APS-GSECARS Format: Poster |
| To evaluate the iron and aluminum effects on post-perovskite phase at deep mantle conditions that may be relevant to the seismic anomaly across and with D? layer it is important to study the potential mantle phase containing both iron and aluminum. In this study, three different compositions of garnet along pyrope-almandine join, Pyr21Alm73Gr5, Pyr43Alm54Gr2, Pyr58Alm38Gr3, were used to investigate the stability and elasticity of high iron- and aluminum-bearing post-perovskite phase at deep mantle conditions. In situ high-pressure and high-temperature experiments were conducted at beamline 13-ID-D, GSECARS, Advanced Photon Source. A monochromatic beam with a wavelength of 0.3044 Å was used for X-ray diffraction data collections. Samples were loaded in the symmetrical diamond-anvil cells and heated by the double-sided laser heating system. Our results showed that the post-perovskite phase can be successfully synthesized from three different compositions at pressure greater than 160 GPa and temperature higher than 1600 K. This indicates that the post-perovskite phase can simultaneously accommodate high aluminum and high iron contents. However, Al2O3-post-perovskite phase can also be observed from some runs for Pyr43Alm54Gr2 and Pyr58Alm38Gr3, showing that there is actually a limit for incorporating the aluminum into the post-perovskite phase but not for iron. Besides, we also found that the volume of post-perovskite phase may be affected by the incorporated amount of iron. Our pressure-volume results showed that high-iron post-perovskite phases have larger volumes of post-perovskite phase and the effect is more profound at pressure greater than 120 GPa. |
Pressure dependence of lattice anharmonicity and phonon lifetime in MgO: a first-principles calculation and implications for lattice thermal conductivity |
| Xiaoli Tang Auburn University tangxia@auburn.edu Jianjun Dong |
| Facility: None Format: Poster |
| We report a recent first principles calculation of harmonic and anharmonic lattice dynamics of MgO. The 2$^{nd}$ order harmonic and 3$^{rd}$ order anharmonic interatomic interaction terms are computed explicitly, and their pressure dependences are discussed. The phonon mode Gr\"{u}neisen parameters derived based on our calculated 3$^{rd}$ lattice anharmonicity are in good agreement with those estimated using the finite difference method. The phonon lifetime due to lattice anharmonicity is calculated based on the single mode excitation approximation (SMEA). We have further estimated the isotope effect on phonon lifetime within the random mass disorder approximation. The implications for lattice thermal conductivity at high pressure are discussed based on a simple kinetic transport theory. |
Effects of Pressure on MnPS3 |
| Cathy Tarabrella State University of New York, Stony Brook, NY ctarabrella@notes.cc.sunysb.edu Lauren Borkowski (UNLV, Las Vegas, NV), Richard Harrington, and John Parise |
| Facility: Other Format: Poster |
| Transition metal thiophosphates (MPS3; M=Mn, Fe, Cd, Co, Zn) belong to the class of quasi-two-dimensional compounds related to CdI2 structure type. Like many 2-D compounds, MPS3 is characterized by weak van-der-Waals interactions in the inter-layer region and strong ionic intra-layer bonds. Due to the large van-der-Waals gap and variable oxidation state of transition elements in the layers (Mn, Fe Co), these materials can easily be intercalated with alkali metal and organic cations to produce compounds with interesting magnetic and chromophoric properties. Previous high pressure studies done on compounds with the same structural topology have lead to interesting structure and property changes which may also be found in transition metal thiophosphates. A preliminary optical investigation at high pressure showed that MnPS3 undergoes a color change from green to red below 10 GPa. Powder diffraction data will be compared with single crystal diamond anvil cell data, which showed an increase in volume between 3.77 GPa and 4.65 GPa. |
Spin transition in ferrous iron in MgSiO3 perovskite under pressure |
| Koichiro Umemoto University of Minnesota umemoto@cems.umn.edu Renata M. Wentzcovitch Yonggang Yu Ryan Requist (Theoretische Festkoerperphysik, Universitaet Erlangen-Nuernberg, Germany) |
| Facility: None Format: Poster |
| We present a density functional study of the pressure-induced spin transition in ferrous iron in MgSiO3 perovskite. We address the influence of iron concentration and configuration (structural and magnetic), as well as technical issues such as the nature of the exchange correlation (XC) functional (CA-LDA versus PBE-GGA) on the spin transition pressure. Supercells containing up to 160 atoms were adopted to tackle these issues. We show that there are preferred configurations for high-spin (HS) and low-spin (LS) iron and that the spin transition pressure depends strongly on iron concentration and all the issues above. Across the spin transition, atomic and electronic structure change significantly. PT range of mixed spin state is estimated. The configurational entropy plays important roles in stabilization of (Mg,Fe)SiO3. Research supported by NSF/EAR 013533, 0230319, and NSF/ITR 0428774 (VLab). Computations were performed at the Minnesota Supercomputing Institute and Indiana University?fs BigRed system. |
High pressure solid-metal/liquid-metal partitioning of Os, Re and Pt in the Fe-FeS system |
| James A Van Orman Case Western Reserve University jav12@cwru.edu Shantanu Keshav (now at Bayerisches Geoinstitut) Yingwei Fei (Geophysical Laboratory) |
| Facility: None Format: Poster |
| Coupled enrichments in 186Os/188Os and 187Os/188Os in some ocean island basalts have been inferred to reflect material transfer from Earth?s outer core to the base of the mantle. The outer core is a viable source for these coupled enrichments if it is able to maintain sufficiently high Pt/Os and Re/Os ratios for sufficient time. Iron meteorite studies and some experimental data indicate that progressive crystallization of the inner core is a plausible mechanism for generating the required high Pt/Os and Re/Os ratios in the outer core. However, the conditions of the experiments and meteorite parent bodies are far different from those in Earth?s core, particularly in terms of pressure. Here we present experimental results on the partitioning of Os, Re and Pt between solid iron and liquid iron sulfide solutions over a wide range of pressures, from 3.3 to 22 GPa. The solid/liquid partition coefficients for these elements decrease, and become more similar to each other, as pressure increases. This behavior is consistent with an increasing misfit of each element in the iron lattice with increasing pressure, due to the small compressibility of Os, Re and Pt relative to iron. The partition coefficients, and differences among them, are too small at the conditions of these experiments to significantly fractionate Re/Os and Pt/Os in the outer core during inner core crystallization. If lattice strain is primarily responsible for the pressure effect, the partition coefficients are expected to decrease further at the higher pressures relevant to the core. Thus, it appears unlikely that crystallization of the inner core is capable of producing an outer core with significantly radiogenic Os isotope ratios. |
X-ray absorption and emission spectroscopy of Fe2O3 to 45 GPa |
| Shibing Wang Department of Applied Physics, Stanford University, Stanford, CA, 94305 shibingw@stanford.edu Wendy L. Mao, Yong Cai (BNL), Nozomu Hiraoka (Taiwan beamline, BL12XU, SPring-8), Yang Ding (HPSynC), Ho-kwang Mao (GL), Jinfu Shu (GL), and Chichang Kao (BNL) |
| Facility: Other Format: Poster |
| As an important earth mineral and archetypal transition metal oxide, hematite (Fe2O3) undergoes a series of electronic transitions and structural changes under high pressure and/or high temperature, which have significance for deep Earth studies and condensed matter physics. At ambient conditions, hematite adopts the Al2O3 structure and is an antiferromagnetic insulator, with five 3d electrons in the high-spin state. Upon increasing pressure, in the 40-70 GPa range, it transforms from a high-spin state to a low-spin state. Here we report experimental results using X-ray absorption spectroscopy and X-ray emission spectroscopy to study the Fe K-edge and K¦Á emission spectra of Fe2O3 to 45GPa. The double-peak structure in the pre-edge region of the Fe K absorption spectrum, resulting from the crystal field splitting energy (CFSE) of octahedrally coordinated Fe3+ were observed in all spectra, with the CFSE increasing with pressure. The intensity of the t2g-related peak became weaker at 45GPa, suggesting an electronic phase transition. The spectral shape of X-ray K¦Á emission also varies with pressure, with the K¦Á1 peak becoming more symmetric as pressure increases. |
Rheology of Basic Granulite: Implications for the Strength of the Continental Lower Crust |
| Yongfeng Wang State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, luckyyfwang1@sina.com Junfeng Zhang(Institute of Geophysics and Planetary Physics and Department of Earth Sciences, University of California, Riverside, CA 92521 USA) Zhenmin Jin Harry W. Green, II(Institute of Geophysics and Planetary Physics and Department of Earth Sciences, University of California, Riverside, CA 92521 USA) |
| Facility: Other Format: Poster |
| Recent years have seen many efforts and debates on the rheological properties of continental lower crust, which is believed to be dominated by basic granulite in composition. The controversy focuses on whether lower crust is strong or weak mechanically when compared with upper mantle and upper crust. That depends on the rheological properties of lower crustal rocks. However, data are still sparse to date on rheology of the lower crust, which restricts understanding of the evolution of continental lithosphere. In this study, we performed experiments to quantify the high pressure and temperature creep behaviors of a two-pyroxene basic granulite (57% Plag + 24% Cpx + 14% Opx + 5% opaque minerals + trace amount of K-feldspar). The experimental starting materials were prepared by hot-pressing of well-mixed fine-grained powders of granulite with grain sizes of 32-53um. Deformation experiments were carried out in a modified Griggs-type apparatus at a confining pressure of 1.1 GPa, temperatures of 1100 K to 1250 K and strain rates of 3.7 X 10-4 s-1 to 9.0 X 10-6 s-1 with the oxygen fugacity buffered at Ni/NiO. The mechanical data are fit by a power law, yielding an activation energy Q = 259 ¡À 52 kJ/mol, a stress exponent n = 3.3 ¡À 0.2, and a preexponential factor lnA = -4.05 ¡À 5.53, suggesting a plastic deformation in the dislocation creep regime. These data suggest that granulite is significantly weaker than dry eclogite, dry clinopyroxenite, and peridotite. A weak lower crust is consistent with the traditional ¡°sandwich¡± model of the strength of continental lithosphere. We hypothesize that the lower crust will decouple from the eclogitic lower crust or the upper mantle when they are subjected to deformation. Delamination may happen between the untransformed granulite and the eclogitic lower crust or the upper mantle in the deep levels of continental crust. |
The Phase Transition and Compressibility in Silicon Nanowires |
| Yuejian Wang Los Alamos National Laboratory yuejianw@lanl.gov Yuejian Wang1,?, Jianzhong Zhang1, Ji Wu2, Jeffrey L. Coffer2, Zhijun Lin2, Stanislav V. Sinogeikin3, Wenge Yang3, Yusheng Zhao1,* 1LANSCE-Division, Los Alamos National Laboratory, NM, 87545 2Department of Chemistry, Texas Christian University, TX 76129 3High Pressure Collaborative Access Team, Advanced Phonon Source, Argonne National Laboratory, Argonne, IL 60439 |
| Facility: APS-HPCAT Format: Poster |
| Silicon Nanowires (Si NMs), one-dimensional single crystalline, have drawn extensive attentions, thanks to their robust application in electrical or optical devices. Another prospective opportunity for Si NWs is to build superhard composites in which Si NWs are inserted into diamond matrix by atomic bonding, like reinforcing steel rods embedded into concrete, to improve the excessive mechanical properties of diamond composites. However, the knowledge on the mechanical properties of Si NWs is very poorly little. Here, we employed advanced photon source and diamond anvil cell to study the phase transitions and to measure the compressibility of Si NWs under high pressure in a hydrostatic or quasi-hydrostatic condition. In comparison with the bulk Si, the high bulk modulus, low Young?s modulus, and structural stability in a broad pressure regime, suggest that Si NWs may be a right material to manufacture the super hard materials used in oil-well exploration industry. The proposed super hard materials with enhanced fracture toughness could improve the drilling efficiency and eventually lower the cost of crude oil production. |
Compressional and Shear Wave Velocities in epsilon-FeSi to 12 GPa |
| Matthew L Whitaker Stony Brook University, Mineral Physics Institute, Stony Brook, NY 11794-2100 matthewlwhitaker@aim.com Liu, Qiong Liu, Wei Wang, Liping Li, Baosheng |
| Facility: NSLS-X17B2 (MAC) Format: Poster |
| Ultrasonic interferometry was used in combination with synchrotron X-radiation to determine the compressional and shear wave velocities and unit-cell volumes of epsilon-FeSi (cubic B20 structure) at room temperature and pressures up to ~12 GPa. The data collected during compression are compared with those collected during decompression after heating to release stress within the sample cell. By fitting all of the decompression unit-cell volume and sound velocity data to third-order finite-strain equations, we obtain the adiabatic zero-pressure bulk and shear moduli and their first pressure derivatives: KS0=169.3(8) GPa, G0=116.3(4) GPa, KS0'=6.5(3), G0'=3.0(1). The bulk modulus obtained from this study is in good agreement with those of some previous experimental studies, but significantly lower than those obtained by first-principles calculations. This study presents the first direct measurement on the shear properties of this phase. |
Olivine H2O storage capacity: effects of temperature, composition and oxygen fugacity |
| Tony Withers University of Minnesota withe012@umn.edu Marc Hirschmann |
| Facility: None Format: Poster |
| Olivine plays an important role in influencing the distribution of H2O in the Earth's mantle. In addition, olivine is expected to be the most abundant phase throughout much of the Martian mantle, and is therefore likely to be an important host of planetary H2O in Mars. The prevailing oxygen fugacity, geothermal gradient and mineral compositions in the Martian mantle are likely to differ from those in Earth, however, so it is important to know the effects of these variations on the H2O storage capacity of olivine. We present H2O storage capacity measurements of olivine equilibrated in multi-anvil experiments at 8 GPa, which suggest that, in contrast to lower pressure data, olivine composition and oxygen fugacity have relatively minor influences on H2O storage capacity. With increasing temperature, however, the H2O storage capacity of olivine is markedly diminished, owing to dilution of the hydrous component in the coexisting fluid/melt. |
An efficient method for calculating the elastic properties at high PT |
| Zhongqing Wu Department of Chemical Engineering and Materials Science and Minnesota Supercomputing Institute, Un wuzq@cems.umn.edu |
| Facility: None Format: Poster |
| First principles quasiharmonic (QHA) calculations play a very important role in mineral physics because it can predict accurately the structure and thermodynamic properties of materials at pressure and temperature conditions that are still challenging for experiments. It also enables calculations of thermoelastic properties by obtaining the second order derivatives of the free energies with respect to Lagrangian strains. However, these are exceedingly demanding computations requiring thousands of large jobs running on 10^1 processors each. Here we introduce a simpler approach that requires only calculations of static elastic constants and phonon vibrational density of state for unstrained configurations. This approach decreases the computational time by more than one order of magnitude. We show results on MgO and forsterite that are in very good agreement with full first principles results and experimental data. |
A simple and effective method for anharmonicity |
| Zhongqing Wu Department of Chemical Engineering and Materials Science and Minnesota Supercomputing Institute, Un wuzq@cems.umn.edu Yonggang Yu, and Renata M. Wentzcovitch |
| Facility: Other Format: Poster |
| Here we develop a method to include the anharmonicity neglected by the quasiharmonic approximation (QHA). The temperature dependence of the renormalized phonon frequency is expressed in an implicit way by volume modification in our method. A reasonable volume modification formula was obtained based on the anharmonicity characteristic. Only parameter introduced in our method is a constant c. The quasiharmonic approximation becomes a special case in our method with c = 0. The method produces the correct the low and high temperature behavior. The thermodynamic properties of MgO (periclase) and Mg2SiO4 (forsterite and wadsleyite) improve very much after including the anharmonic effect. The anharmonic effect has dramatic effect on the phase transformation between forsterite and wadsleyite and can reconcile the discrepancies at the Clapeyron slopes among previous reports. |
The structural evolution of MgSiO3 glass at high pressure and temperature |
| Akihiro Yamada University of California, Davis yamada@geology.ucdavis.edu C.E. Lesher, S.J. Gaudio, T. Inoue(Ehime University) and K. Funakoshi(SPring-8) |
| Facility: Other Format: Poster |
| We have demonstrated the in situ diffraction structural refinement on MgSiO3 glass at room temperature and just below the crystallization temperature for those pressures. The Si-O bond length increases with pressure up to 6 GPa. Whereas, the bond length decreases at least up to 11 GPa. And then that increases at high pressure above 11 GPa. We have interpreted this complex structural evolution in the local structure as a permanent structural change divided on the boundary of 6 GPa. In order to check this interpretation, the Raman spectroscopy has been conducted on the recovered glasses. That indicated the structural difference in the between the glass recovered from lower than 6 GPa and the glass recovered from higher than that condition. To obtain more quantitative information on the local structure in dense MgSiO3 glass, we are performing the NMR spectroscopic analysis on the glasses undergone the high pressure and temperature conditions (just below the crystallization temperature estimated by our in situ experiment). We will present the details on the structural evolution with pressure on MgSiO3 glass, including about the existence of the highly coordinated Si. |
Inelastic X-ray Scattering Capabilities at 3-ID Beamline of Advanced Photon Source |
| Hasan Yavas Department of Geology, University of Illinois at Urbana-Champaign yavas@aps.anl.gov Wolfgang Sturhahn, Advanced Photon Source, Argonne National Laboratory Jay Bass, Department of Geology, University of Illinois at Urbana-Champaign Jennifer Jackson, California Institute of Technology Ahmet Alatas, Advanced Photon Source, Argonne National Laboratory Ercan Alp, Advanced Photon Source, Argonne National Laboratory Jiyong Zhao, Advanced Photon Source, Argonne National Laboratory Michael Lerche, HP Sync, Carnegie Institution for Science |
| Facility: Other Format: Poster |
| High-resolution Inelastic X-ray Scattering (IXS) techniques offer new and exciting results on the properties of materials at extreme conditions like high pressure and temperature. Such experiments have become feasible due to the characteristics of third-generation synchrotron radiation sources such as the Advanced Photon Source, ESRF and Spring8. The IXS techniques can be categorized into three broad areas: ? Momentum-resolved Inelastic X-ray Scattering directly gives the dispersion relation of low-energy collective excitations like phonons. Such measurements provide directional information on vibrational and elastic properties, such as the elastic tensor and sound velocities. ? Synchrotron Mössbauer Spectroscopy (SMS) provides information on magnetic properties and valence state of iron in minerals and high-pressure phases. It is also sensitive to solid-melt transitions. ? Nuclear Resonant Inelastic X-ray Scattering (NRIXS) provides information on vibrational and elastic properties, such as the phonon density of states and sound velocities. All three techniques can be performed using small samples in a diamond anvil cell (DAC). It is desirable to characterize materials by IXS techniques while they are at high pressure and high temperature conditions, similar to those in the deep earth. For this purpose a laser heating system was installed for SMS and NRIXS at sector 3-ID at the Advanced Photon Source. At the moment external heating method is employed for momentum-resolved measurements. The developments and planned improvements at the 3-ID beamline that are relevant to earth and planetary sciences will be presented. |