High Pressure Melting of the Earth's Core Material

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EAR-0229987ShenThis proposal is to pursue experimental studies of (1) high pressure melting behavior of candidate core materials, and (2) the properties of core-forming liquids at high pressure and high temperature using new synchrotron x-ray diffraction and absorption methods. For the proposed melting studies, the investigators will use the technique they established of identifying the onset of melting by the appearance of diffuse x-ray scattering from the melt with the simultaneous absence of crystalline diffraction. Research will be conducted on core materials using a double-sided laser heated diamond anvil cell system combined with an area detector and synchrotron x-ray beam. At the same time, the melting studies will lead to measurements of diffuse scattering of melts at high pressures by the brilliant synchrotron x-ray beam, providing important information on the local structure of melts and, further, the understanding of related macroscopic properties. Using monochromatic x-ray absorption, densities of core forming liquids at high pressure-temperature conditions will be determined, resulting in pressure-volume-temperature equations of state for melts in the Earth's deep interior. The success of these measurements will provide (1) melting curves for iron and iron alloys, (2) the structure and density of amorphous iron at high pressures and at room temperature, (3) the structure of crystalline iron phase near melting and the local structure of melts above melting, and (4) densities of melts (e.g., Fe-FeS) at high pressures. Combined these results will provide crucial constraints for dynamic, thermal and chemical differentiation models of the Earth.--