Towards reconciling experimental and computational determinations of Earth's core thermal conductivity
Towards reconciling experimental and computational determinations of Earth's core thermal conductivity
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DOI：
10.1016/j.epsl.2022.117466
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发表时间：
2022-04
影响因子：
5.3
通讯作者：
M. Pozzo;C. Davies;D. Alfé
中科院分区：
文献类型：
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作者：
M. Pozzo;C. Davies;D. Alfé
地球核心的热导率（κ）是控制核心冷却速率、内核年龄和地球发电机可用功率预测的关键参数。然而，从最近的研究中推断的核心热导率的值跨越了很宽的范围，由于外推到核心液体的压力-温度-组成（PTC）条件的挑战。特别是，从直接实验测定的κ外推低于在核心条件下进行的从头计算。我们已经进行了密度泛函理论（DFT）计算，以确定在温度（850-4350 K）和压力（60-144 GPa）范围内的两种成分，4 mol%和15 mol% Si的固体FeSi合金的热导率和电阻率（ρ），以便于与最近直接测量的κ值进行比较。与最近的实验相一致，我们的计算表明，对于较大的Si组合物的混合物的电阻率大幅增加，相比，纯Fe，达到其饱和值已经在最低温度调查。结果，混合物的导热率也相应地降低。我们还分析了由于忽略电子-电子散射（EES）过程而在DFT计算中可能产生的误差的影响。我们的研究结果表明，实验和EES-corrected DFT计算的κ实际上是一致的不确定性直接比较重叠PTC条件。我们使用我们在核幔边界（CMB）条件下修正的估计值κ= 75− 81 W m− 1 K− 1，提出了新的地核热历史模型，这支持了之前关于大约4亿至7亿年前的晚期内核形成和早期熔融下地幔的确定。
The thermal conductivity (κ) of Earth's core is a critical parameter that controls predictions of core cooling rate, inner core age and the power available to the geodynamo. However, the values of core thermal conductivity inferred from recent studies span a wide range due to the challenges of extrapolating to the pressure-temperature-composition (PTC) conditions of the core liquid. In particular, extrapolations of κ from direct experimental determinations are lower than ab initio calculations conducted at core conditions. We have performed density functional theory (DFT) calculations to determine the thermal conductivity and resistivity (ρ) of solid FeSi alloys with two compositions, 4 mol% and 15 mol% Si, at a range of temperatures (850-4350 K) and pressures (60-144 GPa) for ease of comparison with recent directly measured κ values. In agreement with recent experiments, our calculations show that for the larger Si composition the resistivity of the mixture increases substantially, compared to pure Fe, reaching its saturated value already at the lowest temperature investigated. As a result, the thermal conductivity of the mixture is also correspondingly reduced. We also analysed the effect of possible errors in the DFT calculations due to the neglect of electron-electron scattering (EES) processes. Our results show that experimental and EES-corrected DFT calculations of κ are actually consistent within uncertainties when compared directly at overlapping PTC conditions. We present new core thermal history models using our EES-corrected estimates of κ= 75− 81 W m− 1 K− 1 at core-mantle boundary (CMB) conditions, which support previous determinations of late inner core formation around 400-700 Myrs ago and an early molten lower mantle.