Elasticity Grand Challenge Workshop
Abstracts
Hints from Mother Earth: Challenge is to Unravel the Clues:
How can Elasticity Grand Challenge Project and COMPRES Contribute to this Story?
Robert C. Liebermann
COMPRES,
Progress in understanding the observational data for the Earth’s interior [e.g., from studies in seismology and geodynamics] rests critically on an improved knowledge of the elastic properties of minerals and rocks at elevated pressures and temperatures, using both experimental and theoretical techniques. This has been true for more than 300 years.
COMPRES exists to provide access for the Earth Science
community to the specialized resources at national laboratories for synchrotron
and neutron radiation, as well as nurturing development projects which will
enhance the usefulness of these national facilities for experimental projects.
Individual and collaborative scientific projects [such as the Elasticity Grand Challenge project] are the fundamental building blocks which justify the investment in COMPRES type consortia. The justification for collaborative scientific projects, such as the Elasticity Grand Challenge, is that progress will be achieved more rapidly by virtue of coordination in the planning and execution of new experiments and theoretical calculations.
Stas Sinogeikin, Dmitry Lakshtanov, Jennifer Jackson and Jay Bass
Department of Geology,
A range of samp[les that can be
characterized by Brillouin spectroscopy includes transparent and opaque materials,
single crystals, polycrystalline, and liquid samples. A main advantage of
measuring elastic properties by Brillouin scattering is that small samples can be used (with a thickness of less
than 10 μm and lateral
dimensions of 50x50 μm
or smaller). Brillouin measurements are readily performed in a diamond anvil
cell at high pressures corresponding to that of the lower mantle.
High-temperature measurements can be performed using either electrical
resistance heaters (T>1800 K) and laser heating (T>2500 K). Brillouin
scattering can be combined with
synchrotron XRD and other experimental techniques (e.g. Raman
scattering) for simultaneous measurements at high pressures and/or temperatures.
Our emphasis is now is on increasing pressure and temperature limits of
Brillouin measurements, performing elasticity measurements simultaneously at
high pressures and temperatures, and advancing the technology of working with
samples not possible before (polycrystals, opaque materials).
In this talk we briefly review some
recent developments, advances and challenges in Brillouin scattering and
discuss the results of interlaboratory comparisons and cross-calibrations of
Brillouin measurements at high pressures and temperatures on single-crystal and
polycrystalline samples (e.g. MgO, (Mg,Fe)O, majorite-pyrope solid solutions,
and others) with other techniques.
Dmitry L. Lakshtanov, Stanislav V. Sinogeikin, Jennifer M. Jackson, and Jay D. Bass.
This talk focuses on advances in measuring sound velocities and elastic moduli at high temperatures using Brillouin scattering. We have developed techniques for determining elastic properties at high temperatures using both external (to 1800K) and laser heating (to T > 2500K). The full set of elastic moduli of transparent and translucent materials at high temperatures can be measured on samples with dimensions smaller than 50x50x10mm. Compact resistance heaters of our design were used to study temperature dependence of elastic moduli as well as observation of phase transitions in variety of silicate, oxide materials and glasses. The combination of Brillouin scattering with CO2 laser-heating allowed us to perform acoustic velocities measurement up to 2500(100)K on single-crystal MgO. Both Brillouin and Raman scattering were performed simultaneously on laser-heated samples of single-crystal Al2O3 to temperatures exceeding 2000(100)K. Our results show, that both, resistive and laser-heating can be successfully coupled with Brillouin (and Raman) scattering for accurate determination of elastic properties of silicate and oxide phases at a temperature range characteristic for the Earth crust and mantle.
Brillouin measurements on polycrystalline silicates
Jennifer M. Jackson, Stanislav V. Sinogeikin, Jianzhong Zhang, and Jay D. Bass
Brillouin scattering is an optical spectroscopic method that measures the sound velocities of material. In the past, most Brillouin studies have focused on measurements of single crystals. These studies have been done on numerous minerals, high-pressure phases, and analogue compounds exhibiting a wide range of elastic anisotropy (e.g., pyroxenes, garnets, olivine, ringwoodite, and ferropericlase). However, many high-pressure and/or high-temperature phases of interest remain difficult to synthesize as single crystals of adequate dimensions for Brillouin investigations. In fact, even the synthesis of well-sintered polycrystalline aggregates of these phases is also quite challenging. In the spirit of the goals put forward by the Elasticity Grand Challenge, we have collaborated with Stony Brook to obtain high-quality polycrystalline materials, such as majorite and silicate perovskite. Brillouin measurements have been made on the polycrystalline samples of MgSiO3-Mg2Si3Al2O12 majorite-pyrope solid solution (Mj-Py), MgSiO3 perovskite (Mg-Pv), and aluminous MgSiO3 perovskite (Al-Pv). In the case of Mg-Pv, where we have obtained single-crystals, we obtain excellent agreement with the aggregate sound velocities measured from the polycrystalline and single-crystal samples. The perovskite results represent the first polycrystalline Brillouin measurements on a dense, anisotropic material characteristic of Earth’s lower mantle and thus represent a major step forward in the area of deep Earth mineral physics. This technical achievement greatly increases the range of materials that can be used for inter-laboratory comparisons with Brillouin scattering. We will discuss the results obtained thus far, and possible future directions and collaborative work.
Elasticity changes with order-disorder processes in earth minerals
Sytle M. Antao, Jennifer Kung, Robert C. Liebermann, Yanbin Wang, and John B. Parise
Mineral Physics Institute and Department of Geosciences,
State
The state of cation disorder has effects on molar volume, thermal expansion, as well as elastic properties in minerals such as spinels, carbonates, and pyroxenes, where a range of ordered states exist (Hazen and Yang 1997). Most experiments on the effect of order-disorder at high pressure were studied on quenched specimens. Therefore, it is important to determine the P-V-T-x EOS, where x is the order parameter by monitoring the structural state in situ. Furthermore, the variation of cation distribution would result in EOS and elastic properties to differ significantly from isostructural values (Hazen and Yang 1999). Recent in-situ acoustic data were obtained at 13-BMD beamline at GSECARS, APS, at about 8 GPa and variable temperatures up to about 1100 °C on MgFe2O4 spinel. Acoustic data were also collected as a function of time to test if cation re-equilibration causes changes in ultrasonic signatures. Preliminary investigations show that a S-wave velocity anomaly starts at about 900 °C, while the P wave is still observed. This effect is not an experimental artifact as the ultrasonics system is proven to be stable up to about 1250 °C.
Elasticity of polycrystalline perovskite NaMgF3 near phase transition
C. David Martin, Jennifer Kung, Baosheng Li, Donald J. Weidner, Robert C. Leibermann, John B. Parise
Earth’s lower mantle is expected to be dominated by magnesium bearing silicate perovskite and speculation surrounds the possibility for phase transformations at lower mantle conditions. However, it is very difficult for current experimental techniques to reach the extreme pressures and temperatures of the lower mantle. An alternative approach uses isostructural analogues to study changes in the perovskite structure at lower P/T conditions. Neighborite (NaMgF3) is isostructural and isoelectronic MgSiO3, making it an excellent analogue material. Previous studies show Neighborite transforms directly from orthorhombic (Pbnm) to cubic (Pm-3m). Ultrasonic techniques have been coupled with X-radiation in a DIA-type cubic anvil high-pressure apparatus to study the polycrystalline elasticity and elastic behavior of NaMgF3 across the phase transition. Data is reported from three separate experiments which encompass both orthorhombic (Pbnm) and cubic (Pm-3m) regions of NaMgF3. Before crossing the phase transition we have observed anomalous acoustic behavior. The results will be presented in this meeting.
Elasticity of Polycrystalline Pyrope (Mg3Al2Si3O12) to 9 GPa and 1000° C by Ultrasonic Inteferometry with Synchrotron X-radiation.
G. D. Gwanmesia1, J. Zhang2, K. Darling3,
J. Kung2,3, B. Li2,3, L. Wang2,3, M. Vaughan 2,3,
J. Chen2,3, D.J. Weidner2,3 , D. Neuville4,
and R. C. Liebermann2,3.
1Department of Physics & Pre-Engineering, Delaware State University, Dover, Delaware 19901, USA; 2Mineral Physics Institute, Stony Brook University, Stony Brook, New York 11974-2100, USA; 3Department of Geoscience, Stony Brook University, Stony Brook, New York 11974-2100, USA; 4Laboratoire de Physique du Globe de Paris, department des Geomaterieux, in France.
Acoustic velocities were measured for synthetic polycrystalline pyrope (Py100) to 9 GPa, and temperatures up to 1000˚C by ultrasonic interferometric technique combined with energy-dispersive synchrotron X-ray diffraction in a cubic anvil DIA-type apparatus (SAM-85). Sample length at high P and T are directly measured by an X-ray image technique and collaborated with length determination from x-ray diffraction of the sample. Elastic wave travel times and X-ray diffraction data are collected during cooling cycle to minimize effect of non-hydrostatic stress on the measurements. Fitting the high P and T data set to three different equations, have yielded quite consistent elastic bulk and shear moduli [KS = 171 (2) GPa; G = 91 (1) GPa], and their pressure and temperature derivatives [KS' = 4.5 ± 0.3; G' = 1.6 ± 0.2, and (∂KS/∂T) P = -17 (1) MPa/K; (∂G/∂T) P = -11 (1) MPa/K]. By fixing K' at 4.5, the whole data set were fit to a high temperature Birch-Murnaghan (HTBM) equation and to each isothermal P-V-T data separately yielding (∂KT/∂T) P = -23 (3) MPa/K, and (∂KT/∂T) P = –24 (7) MPa/K, respectively, and the thermal expansion a (in K-1) = 2.65 (27) x 10-5 + 5.33 (383) x 10-9. Comparison of Py100 data with those other Py-Mj compositions indicates that the thermal properties are insensitive to majorite content in the garnet along the pyrope-majorite join.
Elasticity measurement of single-crystal MgO in deformation-DIA apparatus
J. Kung, B. Li, W. Liu, L.Wang, M.T. Vaughan, J. Chen, D.J. Weidner
Mineral Physics Institute, Stony Brook University
W.B. Durham
The elasticity of MgO is of fundamental interest to geophysics. Moreover, MgO remains in the NaCl structure to pressures in excess of ~200 GPa, which makes an ideal pressure marker for the pressure range of interest. However, nonhydrostatic conditions in the studies of P-V-T and elasticity measurements can introduce systematic deviations to the pressure in the pressure-density equation of state. A new type of experiment was performed on single-crystal MgO by using ultrasonic measurement interfaced to the deformation-DIA module (D-DIA), conjunction with X-radiation techniques. The D-DIA allows us to control the stress state by controlling the displacements of the anvils independently. The differential stress was measured from the pressure markers, NaCl and MgO, using a multi-element detector combined with a conical slit. With this new set-up, we are able to collect data P-T-Volume-V(P,S)-Stress and can measure the elasticity of materials under quasi-hydrostatic conditions at high pressure and temperature. The results of MgO can be used as inter-laboratory comparison of the pressure scale.
B. Li, J. Kung, R. C. Liebermann, D.J. Weidner
Mineral Physics Institute, SUNY Stony Brook
Y. Wang, T. Uchida
GSECARS,
Elastic behavior and physical properties of Earth minerals as a function of pressure and temperature are needed in interpreting seismic discontinuities and tomographic images. Ultrasonic techniques in conjunction with state-of-the-art synchrotron facilities allow us to conduct simultaneous measurements of sound velocities and crystal structure/unit cell parameters and therefore provide precise determination of the elastic moduli and their pressure and temperature derivatives. These techniques have been successfully applied to the study of phases in the upper mantle and transition zone( forsterite, wadsleyite and ringwoodite of (MgFe)2SiO4, MgSiO3 pyroxenes). Here we present our effort in expanding these measurements towards the pressure and temperature conditions of the lower mantle as well as absolute pressure determination using these combined acoustic and P-V-T data. Phase transition and acoustic velocities of unquenchable CaSiO3 perovskite have been determined to 17 GPa 1200 K. Simultaneous sound velocity and X-radiation measurements (P-V-Vp-Vs-T-L) at pressures greater than >20 GPa will be demonstrated by resent measurements on ~1 mm-sized mantle silicate samples.
Steven Jacobsen
Geophysical Laboratory, Carnegie Institution of
A second-generation gigahertz ultrasonic interferometer especially well-suited for determining the elastic tensor of oxides and metals in the 50-100 GPa range is under development at the Geophysical Lab. This major elasticity grand challenge aims to take advantage of new large-volume diamond (or gem) anvil cells and gas-loading single-crystal samples to P > 50 GPa. An important step in this direction was achieved in 2002-2003 when we added GHz-shear to our high-pressure capabilities. The interferometer is being constructed around a high-resolution Raman scattering system for high P-T calibration and experiments. Some new results will be presented on pressure-induced shear-mode softening in several dense oxides such as wüstite, magnesiowüstite and magnetite in the 10 GPa range.
In collaboration with colleagues in
Latest Accomplishments and Upcoming Challenges in Theoretical Planetary Materials Science
Renata Wentzcovitch
Department of Chemical Engineering and Materials Science
and
First principles theory of Earth and planetary materials has emerged in the last decade as a powerful addition to experimental high-pressure techniques in mineral physics. Today, thermoelasticity of minerals, single element partitioning between liquid and solid iron, and phase transition in minerals, without any input, at planetary interior conditions are well documented. These were unthinkable ten years ago. Extrapolation of these successes indicates that in ten years we will have 1) overcome fundamental theoretical difficulties faced today, 2) addressed properties other than those that have been addressed so far, and 3) performed simulations that are larger by orders of magnitude than those that are the norm today. I will review some of the latest accomplishments, outline some scientific grand-challenges, and propose some worthy joint experimental/theoretical enterprises for the upcoming years.
Amorphization in quenched ice-VIII: a first principles study
Koichiro Umemoto and Renata M. Wentzcovitch
Department of Chemical Engineering and Materials Science,
Pressure-induced amorphization is one of the intriguing facts common to H2O-ice and silica. It was first observed in ordinary ice Ih under pressure at 77K, but has been more extensively investigated in a–quartz at room temperature. Despite all progress and effort to understand amorphizaton, a consensus has not been reached yet about its root-cause. Here we investigate by first principles a phenomenon that has been proposed to cause amorphization in a–quartz and has not been demonstrated yet in any system that amorphizes: acoustic phonon collapse, i.e., the instability of entire acoustic branches, or nearly so. The relationship between this phenomenon and amorphization is clearly demonstrated in this study of the structural, mechanical, and vibrational properties of ice VIII under decompression. This is a quenchable high-pressure phase of ice that upon heating to ~130K at 0 kbar undergoes amorphization.
[Supported by NSF-COMPRES and Minnesota Supercomputer Institute]
Low-to-high density phase transitions in ice
Renata M. Wentzcovitch and Koichiro Umemoto
Department of Chemical Engineering and Materials Science,
We have investigated through first principles computations the pressure induced behavior of ice XI and ice VIII. They are, respectively, prototypical low and high density hydrogen-ordered forms of ice consisting of one and two interpenetrating hydrogen-bonded networks, that amorphize within each other' stability field. We have found that: 1) entire acoustic branches soften signaling to amorphization before the low-to-high density transformations occur. This has been observed in ice VIII, but not yet in ice XI. 2) These low-to-high density transformations tend to preserve the style of electric dipole orientation. 3) In this process we have synthesized computationally antiferroelectric ice XI-like and ferroelectric ice VIII-like phases, which are metastable with respect to the truly stable phases, ferroelectric ice XI and antiferroelectric ice VIII.
[Supported by NSF-COMPRES and Minnesota Supercomputer Institute]
Equation
of State of
N.L. Ross1 , N. Bolfan-Casanova2 and C. Vanpeteghem3
1Department of Geosciences, Virginia Tech
2Laboratoire Magmas et Volcans, Université Blaise Pascal
3Department of Geology,
Recently there has been much interest in investigating the effects of minor components, especially Al3+, on the equation of state of MgSiO3 perovskite. However, in order to determine the effect that such minor components have on the compressibility of MgSiO3 perovskite, it is necessary to compare the results with the pure endmember. Although MgSiO3 perovskite has been the subject of numerous experimental studies, values of the bulk modulus of MgSiO3 perovskite show a significant range from the commonly accepted value of 265 GPa. In this talk, we present an equation of state for MgSiO3 perovskite determined from recent high-pressure single-crystal X-ray diffraction experiments that are consistent with Sinogeiken et al.’s (2004) recent determination of KS = 253(3) GPa from Brillouin spectroscopy. We shall also review the different methods and techniques that have been used to determine the equation of state of MgSiO3 perovskite, providing a basis for discussion of the elastic properties of MgSiO3 perovskite and potential for interlaboratory comparisons.
Standard materials for calibrating high-pressure apparatus.
R.J. Angel
Virginia Tech Crystallography Laboratory, Department of Geosciences, Virginia Tech, Blacksburg, VA 24060, USA, rangel@vt.edu
Pressure is defined in terms of fundamental SI units, so the terms “pressure standard” and “pressure calibration” are meaningless unless one chooses to redefine the SI base units of length, mass, or time. What is, however, required are materials whose physical properties change in a known way so that the measured changes in these properties can be used to calibrate high pressure, or high pressure-temperature, apparatus.
For a material to be useful as a calibrant it should be of having reproducible properties independent of the physical form of the sample, and or the method of synthesis. It must have a variety of physical properties that vary strongly with pressure so that the sample can be used to calibrate, and cross-calibrate, different types of experimental apparatus. Some of the detailed requirements will be reviewed and offered for discussion in this presentation.
Pressure Scales at High Temperatures in Multi-anvil Apparatus
J. Li1,2, Y. Fei1, C. Hadidacos1, R. Hemley1, H. Mao1, K. Hirose3, W. Minarik1,4, J. Van Orman1,5, C. Sanloup1,6, M. Walter7, T. Komabayashi3, K. Funakoshi8
1Carnegie Institution of
2University of
3Tokyo
5Case
6Université
8Japan Synchrotron Radiation Research Institute
In order to evaluate the accuracy and precision of pressures scales at high temperatures in multi-anvil apparatus, we conducted experiments using multiple internal pressure standards including Au, Pt, MgO, W, Mo, Pd, and Ag. Our data revealed large discrepancies in pressure determination using different pressure standards, or different thermal equations of state for the same standard. Using the MgO scale of {J. Geophys. Res. 106(2001)515} as a reference pressure scale, new Au and Pt scales are presented that are consistent with the MgO scale. Additional uncertainties in high-temperature pressure scales come from temperature measurements under high pressure. We studied the behavior of type C_Re/W and type S_Pt/Rh thermocouples in a multi-anvil apparatus and characterized the errors in temperature measurements due to the effect of pressure on the thermocouple emf (electro-motive-force) and the mechanical and chemical instabilities of the thermal elements.
Some Limitations of Radial Diffraction Measurement of Elastic Properties
Donald J. Weidner and Li Li
Department of Geosciences, State
It has become routine to measure the differential strain field in both diamond anvil and multi-anvil cells using synchrotron x-rays. In these experiments, the x-rays pass through the sample along a path perpendicular to the compressive axis of a cylindrical stress field. Then the diffracted x-rays sample the lattice spacings both parallel and perpendicular to the maximum stress. Detection can be by means of a 2-D system such as an imaging plate or a CCD detector with monochromatic x-rays, where the Debye rings are recorded as a function of the azimuthal angle, c. Then the lattice spacings parallel to the maximum stress axis at c = 0° can be compared with those parallel to minimum stress axis at c = 90°. White x-rays provide the same results with multiple solid state detectors, used in conjunction with a conical slit, located at c = 0° and c = 90°. These measurements have been possible with the use of x-ray transparent gaskets, usually Be for the diamond cell, and x-ray transparent anvils, such as cubic boron nitride, for the multi-anvil system.
Each diffraction line will give rise to a measure of the
stress field in the sample, giving stress measures for distinct populations of
grains, namely those whose orientations meet the necessary diffraction
conditions. If the sample has been compressed and strained elastically, then the
Reuss – Voight bounds become the defining relationship among the stress –
strain fields of the different populations of grains that are sampled by x-ray
diffraction lines. Singh indicates the relationship between the strain field
and the average stress field using the parameter, a = 1 to indicate a ‘Reuss’ solid (uniform stress) and a = 0 indicating a ‘Voight’ solid (uniform
strain). A value between 0 and 1 indicates a mixed boundary
condition solid. However, when the polycrystal is plastically deformed, several
important changes occur. First, the x-ray diffraction is only sampling a
portion of the total strain field. It does not reflect the plastic
portion. Second, the stress in an individual grain is no longer controlled by
the elastic properties, but rather by the plastic properties. The Schmidt
factor, which represents the ratio of a stress on a dislocation to the stress
on the grain, becomes the relevant measure of anisotropy and the stress fields
in the different grain populations now evolve to maintain the necessary stress
on the dislocations as to enable plastic deformation. The
Last modified 5/7/2004 11:51 AM