Collaborative Research: Elasticity Grand Challenge of the COMPRES Initiative

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Hemley0135540Elasticity measurements on minerals are the bridge between the observed seismic velocity structure of the Earth and properties of the Earth at depth, such as chemical composition and temperature. The mineral physics community is poised to undertake a new generation of experiments, which will allow us to accurately determine the properties of deep-Earth materials under a new regime of pressure and temperature (P-T) conditions. We will undertake a coordinated, multi-institutional effort to develop advanced experimental and theoretical techniques for determining sound velocities and elastic moduli on Earth materials. We will build on the current technology that utilizes light scattering and ultrasonic methods and exploit the full use of synchrotron radiation facilities for simultaneous characterization. We will pursue new methodologies utilizing inelastic x-ray scattering or gigahertz ultrasonics to expand the current capabilities. We will closely integrate theoretical approaches with the experimental to ground-truth both. Using multiple techniques, including theoretical calculations, we will focus our efforts on determining the elastic properties of olivine and its high-pressure polymorphs under high P-T conditions, and standard materials for high P-T calibrations (e.g., Pt, Au, MgO, NACI). Samples will be synthesized at a central community facility. The accuracy of each technique will be improved through inter-laboratory cross-checks and comparison with theory. This collaborative approach will greatly advance the technology of high pressure geophysics, and focus a community effort on accurate determination of the elastic properties of the most important mantle phases. These results will, in turn, be used to clarify our view of mantle composition and thermal structure.