Ab Initio Molecular Dynamics Investigation of Molten Fe-Si-O in Earth's Core
Ab Initio Molecular Dynamics Investigation of Molten Fe-Si-O in Earth's Core
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DOI：
10.1029/2019gl082722
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发表时间：
2019-06-28
影响因子：
5.2
通讯作者：
Li, Yunguo
中科院分区：
文献类型：
--
作者：
Huang, Dongyang;Badro, James;Li, Yunguo
硅和氧是地核中潜在的轻元素，因为随着温度的升高，它们对金属的亲和力更强，这意味着大量的硅和氧可以被并入地核。有人提出，Fe-Si-O液态合金可以在长期冷却过程中排出核幔边界处的SiO2，使核中要么有硅，要么有氧，而不是两者都有。最近的一项研究表明，在Fe-Si-O系统中没有出溶，但不溶。本文用从头算分子动力学方法研究了核幔边界压力和温度下Fe-Si和Fe-O双星以及Fe-Si-O三元双星的液相线场。我们发现，液体保持良好的混合与三元属性相同的二元属性的混合。固态SiO2和液态Fe的两相模拟表明，在4100 K以上的温度下，SiO2结晶以及Fe-Si-O中的液态不溶性不太可能发生在地核中。
Silicon and oxygen are potential light elements in Earth's core because their stronger affinity to metal observed with increasing temperature posits that significant amounts of both can be incorporated into the core. It was proposed that an Fe-Si-O liquid alloy could expel SiO2 at the core-mantle boundary during secular cooling, leaving the core with either silicon or oxygen, not both. This was recently challenged in a study showing no exsolution but immiscibility in the Fe-Si-O system. Here we investigate the liquidus field of Fe-Si and Fe-O binaries and Fe-Si-O ternaries at core-mantle boundary pressures and temperatures using ab initio molecular dynamics. We find that the liquids remain well mixed with ternary properties identical to mixing of binary properties. Two-phase simulations of solid SiO2 and liquid Fe show dissolution at temperatures above 4100 K, suggesting that SiO2 crystallization as well as liquid immiscibility in Fe-Si-O is unlikely to occur in Earth's core.