K-Fe Sulfides and Fe-Ni Phosphides at Core Pressures and Temperatures

在地核压力和温度下，地核的密度比纯镍铁的密度低约10%。已经提出了几种元素来解释堆芯密度低的原因，包括硫、硅、碳、钾、氢和氧。由于地幔中的钾和磷都是枯竭的，有人提出这种枯竭可能是由于这些元素并入地核造成的。然而，只有在相对较低的压力和陨石中才能知道含有这些元素的相，而在较高的压力和温度下很少或根本没有实验工作，特别是在接近核心条件的情况下。因此，我们将研究在核心条件下可能存在的两类不同相--钾-铁硫化物和铁-镍磷化物--的高压、高温化学和结构。通过这些实验，我们期望提供关于这些材料的合成、它们的相关系和它们的结构特征的信息。我们还将研究在S和/或C存在或不存在的情况下，K和P在块状硅酸盐土壤和金属液体之间的分配。实验技术将包括在受控蒸汽压、温度和总压力下合成合适的材料，用电子和离子微探针对产品进行表征，以及在高压和高温下使用我们实验室和国家同步加速器源的X射线衍射以及各种光谱技术进行原位结构测量。

EAR-0073433PrewittThe density of the Earth's core is about 10% less than that of pure nickel-iron at core pressures and temperatures. Several elements have been proposed to account for the low density of the core, including sulfur, silicon, carbon, potassium, hydrogen, and oxygen. Because potassium and phosphorous are depleted in the Earth's mantle, it has been proposed that this depletion may result from incorporation of these elements in Earth's core. However, phases with compositions including these elements are known only from syntheses at relatively low pressures and from meteorites, and there has been little or no experimental work at higher pressures and temperatures, especially those approaching core conditions. Therefore, we will investigate the high-pressure, high-temperature chemistry and structures of two different classes of phases that could be present under core conditions, potassium-iron sulfides and iron-nickel phosphides. From these experiments, we expect to provide information on the synthesis of these materials, their phase relations, and their structural characteristics. We also will investigate the partitioning of K and P between bulk silicate earth and metallic liquids in the presence or absence of S and/or C. Experimental techniques will include synthesis of appropriate materials under controlled vapor pressures, temperature, and overall pressure, characterization of products with electron and ion microprobes, and in-situ structural measurements at high-pressures and temperatures using x-ray diffraction in our laboratory and at national synchrotron sources, and by a variety of spectroscopic techniques.