Research News

 

*      Congratulations to Bob Liebermann for AGU Edward A. Flinn III Award!

    

 

                    Link to AGU Website for the Announcement

 

*      Origin of Termal and Compositional Heterogeneities in the Lower Mantle

                    The relative changes between shear and compressional velocities (RSP=∂lnVS/∂lnVP), bulk sound and shear velocities(RCS = ∂lnVC/∂ln VS), and density versus shear wave velocity (RrS=∂ lnr/∂lnVS) in response to thermal and chemical variations were investigated for pyrolitic lower mantle. For heterogeneities with thermal origins, RSP increases from 1.7 to 2.0 together with RrS decreasing from 0.4 to 0.2 and RCS = ~0.27 from the top to the bottom of the lower mantle. In comparison, chemical variations (bulk iron or silica contents) are characterized by RSP < 1.5 and RCS > 0.5 at lower mantle depths. Negative values of RrS and RCS are indicative of chemical anomalies in the lower mantle, but a combination of thermal and chemical heterogeneities may be required to produce velocity and density anomalies at the magnitudes observed in seismic data. (link to Li, B. Progress in Natural Science 19,1603-1611)

 

*    Equation of State of Bulk Metallic Glass: Compressional (VP) and shear wave (VS) velocities Description: Description: Fig2-densityof Zr46Cu37.6Ag8.4Al8 bulk metallic glass (BMG) have been measured up to 6.3 GPa at room temperature using ultrasonic interferometry in conjunction with synchrotron x-radiography. Through an integration with respect to pressure, the densities at high pressures are uniquely determined using the measured velocities. The correlation of the experimental results for the elastic moduli of Zr46Cu37.6Ag8.4Al8 with  the properties of its constituent element metal phases are explored. This work is supported by DOE/NNSA. Details can be found in the publication: Liu, Wei, Q. Zeng, Q. Jiang, Liping Wang, and Baosheng Li (2011) Density and elasticity of Zr46Cu37.6Ag8.4Al8 bulk metallic glass at high pressure, Scripta Materialia 65, 497-500. 

 

 

*    Thermal Equation of State of CaIrO3 Post-Perovskite

Abstract The pressure–volume–temperature (P–V–T) relation of CaIrO3 post-perovskite (ppv) was measured at pressures and temperatures up to 8.6 GPa and 1,273 K,respectively, with energy-dispersive synchrotron X-ray diffraction using a DIA-type, cubic-anvil  apparatus (SAM85). Unit-cell dimensions were derived from the LeBail full profile refinement technique, and the results were fitted using the third-order Birth-Murnaghan equation of state. The derived bulk modulus KT0 at ambient pressure and temperature is 168.3 ± 7.1 GPa with a pressure derivative K0T 0 = 5.4 ± 0.7. All of the high temperature data, combined with previous experimental data, are fitted using the high-temperature Birch-Murnaghan equation of state, the thermal pressure approach, and the Mie-Gru¨neisen-Debye formalism. This work is supported by NSF/Geophysics-Geochemistry.  Liu, W., Whitaker, M., Q. Liu, N. Nishiyama, Y. Wang, A. Kubo, T. Duffy, B. Li, (2011) Thermal Equation of State of CaIrO3 Post-Perovskite, Phys. Chem. Min, DOI: 10.1007/s00269-010-0414-z)

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