Carbon Partitioning Between the Earth's Inner and Outer Core
Carbon Partitioning Between the Earth's Inner and Outer Core
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DOI：
10.1029/2019jb018789
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发表时间：
2019-12-01
影响因子：
3.9
通讯作者：
Brodholt, John
中科院分区：
文献类型：
--
作者：
Li, Yunguo;Vocadlo, Lidunka;Brodholt, John
了解地核中轻元素的丰度和分布是了解地球和其他行星系统的基础。最近的研究（Li et al., 2018; masino et al., 2019）表明碳对解释地核性质特别重要，但对外层和内层地核之间碳分配的了解尚不清楚。利用拟调和近似、从头算分子动力学和热力学积分技术，计算了核心条件下液态Fe和固态hcp-Fe中碳的化学势。我们发现在固体铁中，取代碳比间隙碳和其他碳缺陷簇结构更稳定。晶格应变和过配位效应导致固体铁中C的化学势比液体高，导致碳几乎完全进入液体。我们发现碳可以解释内核边界的大部分密度跳变。这为富氧外核的必要性提供了另一种机制，并可能对地球深部的组成和结构产生重大影响。
Knowledge of the abundance and distribution of light elements in the core is fundamental to the understanding of the Earth and other planetary systems. Recent studies (Li et al., 2018; Mashino et al., 2019) suggest the particular importance of carbon for explaining core properties, yet knowledge of carbon partitioning between the outer and inner core is unknown. By using the quasiharmonic approximation, ab initio molecular dynamics, and thermodynamic integration techniques, we have computed the chemical potential of carbon in liquid Fe and solid hcp-Fe at core conditions. We find that substitutional carbon is more stable than interstitial carbon and other carbon defect cluster structures in solid Fe. Lattice strain and overcoordination effects lead to a high chemical potential of C in solid Fe compared to the liquid, and consequently carbon partitions almost completely into the liquid. We find that carbon can account for most of the density jump at the inner-core boundary. This provides an alternative mechanism to the necessity of an oxygen-rich outer core and may have significant implications for the composition and structure of the deep Earth.