Crystal Buoyancy in the Deep Magma Ocean

今天的地球是一个进化过程的产物，这个过程始于一个大部分或完全熔化的行星。该项目旨在约束早期岩浆海中固相和液相的铁含量。固体在岩浆中是上升还是下沉取决于它们与液体的密度对比，这是它们相对铁含量的函数。铁在两相之间的分配称为配分。量化早期岩浆海洋中的铁分配对于模拟地球地幔向现今结构和成分的演化至关重要。在这里，研究人员使用计算物理学在原子水平上模拟岩浆中铁的化学性质。这个模拟--被称为“从头算”，因为它依赖于量子力学的第一原理--解释了深岩浆海洋中普遍存在的极端压力。该团队最先进的代码包括允许计算铁与固相和液相的亲和力的发展，从而确定矿物质是上升还是下沉。该项目促进了计算矿物物理学研究生的培训。它影响了实验岩石学和地球动力学的邻近领域，对现代地球化学和地震观测的解释具有强烈的影响。它也对材料科学产生了广泛的影响。先前的研究表明，晶体在岩浆海洋中是上升还是下沉，关键取决于铁在液相和晶相之间的分配。然而，在深部岩浆洋条件下，液晶密度差的符号和地球化学演化的矢量是未知的。在这里，PI和他的团队从头开始计算铁在整个下地幔压力体系中共存相之间的分配。该项目代表了密度泛函理论在岩浆海洋中应用的一个重大扩展。它包括端元组成和液体和晶体之间的化学相互作用的研究。该团队在地球含铁系统的从头计算模拟方面取得了成就-包括强相关性和磁熵-通过扩大自由能和元素分配的范围。使用第一性原理分子动力学结合绝热切换，他们将预测铁在以下之间的分配：1）液体和结晶（Mg，Fe）O，2）液体和结晶（Mg，Fe）SiO 3和3）液体近似块状硅酸盐土组成和（Mg，Fe）O铁方镁石和（Mg，铁）的该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查进行评估，被认为值得支持的搜索.

Present-day Earth is the product of an evolutionary process which began with a largely or completely molten planet. This project aims to constrain the iron contents of solid and liquid phases in the early magma ocean. Whether solids rise or sink in a magma depends on their density contrast with the liquid, which is a function of their relative iron contents. The distribution of iron between phases is called partitioning. Quantifying iron partitioning in the early magma ocean is critical to model Earth's mantle evolution toward its present-day structure and composition. Here, the researcher uses computational physics to model at the atomic level the chemistry of iron in the magma. The simulation - called "ab initio" because it relies on quantum-mechanics first principles - accounts for the extreme pressures prevailing in the deep magma ocean. The team's state-of-the-art code includes developments which allow calculating the affinity of iron with solid and liquid phases, thus whether minerals rise or sink. This project promotes the training of a graduate student in computational Mineral Physics. It impacts the adjacent fields of Experimental Petrology and Geodynamics, with strong implications for the interpretation of modern geochemical and seismological observations. It also has broad impacts in Materials Science. Previous work has shown that whether crystals rise or sink in a magma ocean depends critically on the partitioning of iron between liquid and crystalline phases. Yet, the sign of the liquid-crystal density contrast and the vector of geochemical evolution is unknown at the conditions of the deep magma ocean. Here, the PI and his team calculates ab initio the partitioning of iron among coexisting phases throughout the pressure regime of the lower mantle. The project represents a major expansion for the application of density functional theory to the magma ocean. It encompasses studies of end-member compositions and the chemical interaction between liquids and crystals. The team build on their accomplishments in ab initio simulation of Earth's iron-bearing systems - including strong correlation and magnetic entropy - by broadening the scope to account for free energies and element partitioning. Using first principles molecular dynamics coupled with adiabatic switching, they will predict iron partitioning between: 1) liquid and crystalline (Mg,Fe)O , 2) liquid and crystalline (Mg,Fe)SiO3 and 3) a liquid approximating bulk silicate Earth composition and (Mg,Fe)O ferropericlase and (Mg,Fe)SiO3 bridgmanite.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.