Fe-3.24%Si的状态方程和声速的第一性原理计算：地球内核Si元素的约束

李佩芸; 黄海军; 李艳丽

doi:10.11858/gywlxb.20190781

Fe-3.24%Si的状态方程和声速的第一性原理计算：地球内核Si元素的约束

doi: 10.11858/gywlxb.20190781

武汉理工大学理学院，湖北武汉　430070

基金项目: 国家自然科学基金（41874103）；中央高校基本科研经费（2017IB013，2018IB009，2018B011）

详细信息

作者简介:
李佩芸（1994－），女，硕士研究生，主要从事第一性原理计算研究. E-mail：lipeiyun@whut.edu.cn

通讯作者:
李艳丽（1977－），女，博士，副教授，主要从事第一性原理研究.E-mail：liyanli128@whut.edu.cn

中图分类号: O521.2
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出版历程
- 收稿日期: 2019-05-22
- 修回日期: 2019-06-26
- 发布日期: 2019-09-25

First-Principles Calculations of the Equation of State and Sound Velocity of Fe-3.24%Si: Implications for the Composition of Earth’s Inner Core

School of Science, Wuhan University of Technology, Wuhan 430070, China

摘要

摘要: 硅（Si）被认为是地球内核的主要轻元素，但其在内地核中的含量仍然存在争议。为了探索内地核中Si的含量，应用第一性原理方法对Fe-3.24%Si（Si的质量分数为3.24%）进行了研究。构造了4种Fe-3.24%Si的超晶胞，研究了不同的晶胞大小和自旋对优化结构的影响。结果表明：在100 GPa以上，自旋对Fe-3.24%Si的密度无影响；而在100 GPa以下，考虑自旋时的计算结果更接近实验值。基于0 K下的声速、状态方程和相关热力学参数，计算了Fe-3.24%Si在内地核条件下的密度和声速。研究发现：Fe-3.24%Si的密度低于纯铁的密度，略高于内地核的密度；纵波声速及剪切波声速与纯铁的声速很接近，但均明显高于内地核声速，因此排除了内地核含有大量Si元素的可能性。
- Fe-3.24%Si /
- 第一性原理计算 /
- 状态方程 /
- 声速 /
- 内地核
Abstract: Silicon (Si) is considered as one major light element in Earth’s inner core, but its content is still controversy. In order to constrain its content in the inner core, using first-principles calculation method, we constructed four different supercells of Fe-3.24%Si and investigated the effects of cell size and spin on geometry optimization. It is found that the spin doesn’t affect the equation of state of Fe-3.24%Si above 100 GPa, and below 100 GPa, the calculated results with the spin are closer to the experimental data. Based on the equation of state, the sound velocity at 0 K and the corresponding thermodynamic parameters, the density and sound velocity of Fe-3.24%Si are obtained under the conditions of the inner core. The density of Fe-3.24%Si is lower than that of pure iron and slightly higher than that of the inner core. The sound velocities of longitudinal wave and shear wave for Fe-3.24%Si are very close to that of pure iron, but both are significantly higher than that of the inner core. Therefore, we could exclude the possibility that Earth’s inner core contains a large amount of Si.
- Fe-3.24%Si /
- first-principles calculation /
- equation of state /
- sound velocity /
- inner core

HTML全文

图 1 hcp-Fe-3.24%Si的结构

Figure 1. Structure of hcp-Fe-3.24%Si

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图 2 单位体积内的能量e随压力的变化

Figure 2. Variation of the energy per unit volume e versus pressure

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图 3 Fe-3.24%Si的压力随密度的变化

Figure 3. Calculated density vs. pressure for Fe-3.24%Si

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图 4 0 K状态下Fe-3.24%Si的声速与密度的关系

Figure 4. Sound velocity of Fe-3.24%Si versus density at 0 K

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图 5 内地核条件下Fe-3.24%Si的密度、纵波声速v_p、体波声速v_b和横波声速v_s与铁和内地核的数据比较

Figure 5. Comparison of the density, longitudinal sound velocity v_p, bulk sound velocity v_b and shear velocity v_s of Fe-3.24%Si with those of Fe and the data of the inner core

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