Thermal conductivity of Fe-Si alloys and thermal stratification in Earth's core.
Thermal conductivity of Fe-Si alloys and thermal stratification in Earth's core.
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Fe-Si 合金的热导率和地核热分层
DOI：
10.1073/pnas.2119001119
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发表时间：
2022-01-04
影响因子：
11.1
通讯作者：
Lin JF
中科院分区：
文献类型：
--
作者：
Zhang Y;Luo K;Hou M;Driscoll P;Salke NP;Minár J;Prakapenka VB;Greenberg E;Hemley RJ;Cohen RE;Lin JF
地球的液态外核主要由铁合金和8%至10%的轻元素（如硅）组成。液态地核的对流产生了地球磁场，磁场由地核的导热性控制。在这项研究中，我们通过高压和高温实验和数值计算研究了铁硅合金作为地核候选成分的电阻率和导热系数。我们发现在地核压力下，铁硅合金的电阻率几乎与温度无关，因此具有较高的导热性。这项工作表明，如果硅是地核中唯一的主要轻元素，它可以抑制热对流，并促进最外层核的热分层。地核中的轻元素在驱动对流和影响地球动力学方面起着关键作用，这两者对地球动力学都至关重要。然而，铁合金在高压和高温条件下的热输运特性仍然不确定。本文利用激光加热金刚石砧细胞实验、第一性原理分子动力学和动力学平均场理论计算，研究了Si含量为4.3 wt %和9.0 wt %的固态六方致密铁硅合金和液态铁硅合金在高压和高温下的输运性质。与Fe的情况相反，随着Si浓度的增加，Fe-Si合金中的Si杂质散射逐渐主导总散射，导致Fe- 9si中电阻率与温度无关，电子-电子对电导率的贡献较小。我们的结果表明，在最外层核附近，液态Fe-9Si的导热系数为~ 100 ~ 110 W·m−1·K−1。如果地球的核心是由大量的硅（例如，> 4.3 wt %）组成，并且具有如此高的导热率，那么一个亚绝热的热流很可能穿过核心-地幔边界，在核心-地幔边界下留下一个400- 500公里深的热分层层，并且挑战了铁-硅液体外核的热对流。
Earth’s liquid outer core is mainly composed of iron alloyed with ∼8 to 10% of light elements (e.g., silicon). Convection of the liquid core generates Earth’s magnetic field, which is controlled by the thermal conductivity of the core. In this study, we investigated the resistivity and thermal conductivity of iron-silicon alloys as a candidate composition in Earth’s core via high-pressure and -temperature experiments and numerical calculations. We found a near temperature independence of the resistivity in iron-silicon alloys at Earth core’s pressure and thus a high thermal conductivity. This work indicates that if silicon is the sole major light element in Earth’s core it could depress thermal convection and promote a thermally stratified layer at the topmost outer core. Light elements in Earth’s core play a key role in driving convection and influencing geodynamics, both of which are crucial to the geodynamo. However, the thermal transport properties of iron alloys at high-pressure and -temperature conditions remain uncertain. Here we investigate the transport properties of solid hexagonal close-packed and liquid Fe-Si alloys with 4.3 and 9.0 wt % Si at high pressure and temperature using laser-heated diamond anvil cell experiments and first-principles molecular dynamics and dynamical mean field theory calculations. In contrast to the case of Fe, Si impurity scattering gradually dominates the total scattering in Fe-Si alloys with increasing Si concentration, leading to temperature independence of the resistivity and less electron–electron contribution to the conductivity in Fe-9Si. Our results show a thermal conductivity of ∼100 to 110 W⋅m−1⋅K−1 for liquid Fe-9Si near the topmost outer core. If Earth’s core consists of a large amount of silicon (e.g., > 4.3 wt %) with such a high thermal conductivity, a subadiabatic heat flow across the core–mantle boundary is likely, leaving a 400- to 500-km-deep thermally stratified layer below the core–mantle boundary, and challenges proposed thermal convection in Fe-Si liquid outer core.
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影响因子：
13.6
作者：
Clesi V;Bouhifd MA;Bolfan-Casanova N;Manthilake G;Schiavi F;Raepsaet C;Bureau H;Khodja H;Andrault D
通讯作者：
Andrault D
影响因子：
64.8
作者：
Helffrich, George;Kaneshima, Satoshi
通讯作者：
Kaneshima, Satoshi
影响因子：
64.8
作者：
Badro J;Siebert J;Nimmo F
通讯作者：
Nimmo F
影响因子：
--
作者：
GREENWOOD, DA
通讯作者：
GREENWOOD, DA
影响因子：
5.3
作者：
Fischer, Rebecca A.;Campbell, Andrew J.;Prakapenka, Vitali B.
通讯作者：
Prakapenka, Vitali B.