High Pressure Melting of the Earth's Core Material

EAR-0229987申用新的同步辐射X射线衍射法和吸收法对(1)候选岩心材料的高压熔融行为和(2)成核液在高压和高温下的性质进行了实验研究。在拟议的熔化研究中，研究人员将使用他们建立的技术，通过熔体的漫反射x射线散射的出现，同时没有结晶衍射来识别熔化的开始。将使用双面激光加热的金刚石顶锤系统结合面积探测器和同步辐射x射线对核心材料进行研究。同时，熔化研究将导致测量高压下熔体在明亮的同步加速器x射线束下的扩散散射，从而提供关于熔体局部结构的重要信息，并进一步了解相关的宏观性质。利用单色X射线吸收，将确定在高压-温度条件下形成核的液体的密度，从而得出地球深处熔体的压力-体积-温度状态方程。这些测量的成功将提供(1)铁和铁合金的熔化曲线，(2)高压和室温下非晶铁的结构和密度，(3)熔化附近的晶态铁相的结构和熔化以上熔体的局部结构，以及(4)高压下熔体的密度(如Fe-FeS)。综合这些结果，将为地球的动力学、热学和化学分化模型提供关键的约束。

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.--