深部金储层：压力下两种本体不混溶金属的稳定化合物
A deep Aurum reservoir: Stable compounds of two bulk-immiscible metals under pressure
摘要：
众所周知，地壳中的黄金已经耗尽，其他稍微重一些的贵金属是由岩浆从地幔运送到地壳的。块状硅酸盐地球（BSE）模型还表明，硅酸盐地幔本身的金的显着亏损，这不能用地幔岩浆中的金的量来解释。这意味着Au可以保留在下地幔中并形成稳定的化合物，特别是与铁，铁是地核中的主要元素。虽然铁在环境条件下不会与金形成二元化合物或大块合金，但它可能在地球内部的高压下形成。在这里，使用密度泛函方法，我们研究了在高达210 GPa的压力下识别稳定的二元Fe-Au化合物的可能性。我们发现了三个这样的Fe-Au化合物，这是稳定的压力和显着的电子转移，包括正交AuFe $_4$相，这是铁磁性的性质与Au具有显着的磁矩。虽然我们的研究结果表明，由于Fe-Au化合物的传导性和热通量引起的热对流可能是为地球的地球发电机提供动力的能源，但它们也指向Au化学性质的变化，因为它可以在压力下以阴离子或阳离子的形式存在。此外，预测的各种铁金化合物的声速和密度表明，它们可以揭示核幔边界和地球核心的组成，同时证明微量金的存在如何影响与地震数据的一致性。
英文摘要：
The Earth's crust is known to be depleted of gold, among other slightly heavy noble metals transported by magma from the Earth's mantle to the crust. The bulk silicate Earth (BSE) model also suggests significant depletion of Au in the silicate mantle itself, which cannot be explained by the amount of Au in the mantle's magma. This implies that Au could remain in the lower mantle and form stable compounds, especially with iron, which is the predominant element within the core. While Fe does not form binary compounds or a bulk alloy with Au under ambient conditions, it may do so at the elevated pressures found in the Earth's interior. Here, using density-functional methods, we investigated the possibility of identifying stable, binary Fe-Au compounds at pressures up to 210 GPa. We found three such Fe-Au compounds, which are stabilized by pressure and notable electron transfer, including an orthorhombic AuFe$_4$ phase that is ferromagnetic in nature with Au possessing a significant magnetic moment. While our results suggest that thermal convection due to the conductivities and the heat flux from the Fe-Au compounds could be an energy source to power the Earth's geodynamo, they also point towards changes in Au's chemical properties, as it can exist as either an anion or cation under pressure. In addition, the sound velocity and the density predicted for the various Fe-Au compounds suggest that they could shed light on the composition of the core-mantle boundary and the Earth's core, while demonstrating how the presence of trace amounts of Au could influence agreement with seismic data.
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