Thermal Equation of State of Fe3C to 327 GPa and Carbon in the Core
Thermal Equation of State of Fe3C to 327 GPa and Carbon in the Core
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DOI：
10.3390/min9120744
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发表时间：
2019-11
期刊：
影响因子：
2.5
通讯作者：
Suguru Takahashi;E. Ohtani;D. Ikuta;S. Kamada;T. Sakamaki;N. Hirao;Y. Ohishi
中科院分区：
文献类型：
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作者：
Suguru Takahashi;E. Ohtani;D. Ikuta;S. Kamada;T. Sakamaki;N. Hirao;Y. Ohishi
地球内部的密度和声速结构是根据地震观测建模的，被称为初步参考地球模型 (PREM)。地核的密度低于纯铁的密度，这表明地核含有轻元素。碳是一种可能存在于核心中的轻元素。我们基于使用金刚石砧池的原位高压和高温 X 射线衍射实验确定了 Fe3C 的状态方程 (EOS)。我们获得了 Fe3C 在 300 K 下高达 327 GPa 和在 2300 K 下高达 70–180 GPa 的 P-V 数据。非磁性 (NM) Fe3C 的 EOS 通过使用两种不同压力尺度的两个模型来表达，以及 300 K 下的三阶 Birch-Murnaghan EOS 和高温条件下的 Mie-Grüneisen-Debye EOS。使用KBr压力标度，EOS可以用参数V0 = 148.8(±1.0) Å3、K0 = 311.1(±17.1) GPa、K0′ = 3.40(±0.1)、γ0 = 1.06(±0.42)、q = 1.92(±1.73)表示，固定值为θ0 = 314 K （模型1），V0 = 147.3（±1.0）Å3，K0 = 323.0（±16.6）GPa，K0′ = 3.43（±0.09），γ0 = 1.37（±0.33），q = 0.98（±1.01），使用MgO压力标度固定值θ0 = 314 K（模型2）。由 EOS 计算出的内核条件下（假设 P = 329 GPa，T = 5000 K）下 Fe3C 的密度与 PREM 内核兼容。
The density and sound velocity structure of the Earth’s interior is modeled on seismological observations and is known as the preliminary reference Earth model (PREM). The density of the core is lower than that of pure Fe, which suggests that the Earth’s core contains light elements. Carbon is one plausible light element that may exist in the core. We determined the equation of state (EOS) of Fe3C based on in situ high-pressure and high-temperature X-ray diffraction experiments using a diamond anvil cell. We obtained the P–V data of Fe3C up to 327 GPa at 300 K and 70–180 GPa up to around 2300 K. The EOS of nonmagnetic (NM) Fe3C was expressed by two models using two different pressure scales and the third-order Birch–Murnaghan EOS at 300 K with the Mie–Grüneisen–Debye EOS under high-temperature conditions. The EOS can be expressed with parameters of V0 = 148.8(±1.0) Å3, K0 = 311.1(±17.1) GPa, K0′ = 3.40(±0.1), γ0 = 1.06(±0.42), and q = 1.92(±1.73), with a fixed value of θ0 = 314 K using the KBr pressure scale (Model 1), and V0 = 147.3(±1.0) Å3, K0 = 323.0(±16.6) GPa, K0′ = 3.43(±0.09), γ0 = 1.37(±0.33), and q = 0.98(±1.01), with a fixed value of θ0 = 314 K using the MgO pressure scale (Model 2). The density of Fe3C under inner core conditions (assuming P = 329 GPa and T = 5000 K) calculated from the EOS is compatible with the PREM inner core.