CAREER: The influence of cation substitution on the hydrous phases of the lower mantle

事业：阳离子取代对下地幔水相的影响

• 批准号: 2338444
• 负责人: Elizabeth Thompson
• 金额: $ 61.99万
• 依托单位: University of the South
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-06-01 至 2029-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2338444&HistoricalAwards=false
• 关键词: CAREER; influence; cation; substitution; hydrous

Plate tectonics connects the hydrosphere to a water cycle deep in the Earth, as hydrogen-bearing materials are cycled into the planet's interior. The recent discovery of multiple natural diamond inclusions from the deep Earth that contain hydrous phases is compelling evidence that the water cycle of the deep Earth may extend even deeper than was originally believed. This study will use a combination of computational models and experiments to evaluate the stability and geophysical properties of hydrous phases believed to be stable at the conditions of the Earth's lower mantle. Although these are expected to be minor phases, the potential for hydrogen storage in the lower mantle is still considerable, as it comprises approximately 56% of the Earth's volume. This project will fund critical training for an early career scientist who will be guided through learning how to balance teaching, research, and student mentorship at a primarily undergraduate institution. A complementary educational component of this project is to develop a virtual reality application that will help undergraduate geology students develop spatial reasoning skills, with a particular focus on fostering equity and inclusion for neurodiverse students with visual-spatial deficits.Phase D [MgSi2O4(OH)2] and phase H [MgSiO2(OH)2] are dense hydrous magnesium silicates (DHMSs) that are expected to play a key role in the hydrogen cycle of the lower mantle. Importantly, Fe- and Al-substitution has a profound influence on the stability and properties of these phases. In fact, phase H forms a solid solution with d-AlOOH and e-FeOOH, forming a potentially continuous hydrous reservoir with stability down to the core-mantle boundary. This project combines ab initio calculations with high-pressure, high-temperature vibrational spectroscopy and single-crystal X-ray diffraction to evaluate the geophysical properties of intermediate compositions of Al,Fe-bearing phase D and phase H, and to probe how cation substitution affects pressure-induced hydrogen bond symmetrization, which can have a substantial influence on the bulk modulus and its pressure derivative. First principle calculations will systematically evaluate how cation substitution influences the pressure-dependent properties and hydrogen accommodation in these phases, providing a theoretical framework for high-pressure experiments. Combining crystallographic and spectroscopic approaches will provide detailed information on the interatomic forces and bonding environments of hydrogen within these phases, helping explain why these phases are stable at extreme pressures and temperatures.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.

板块构造将水圈连接到地球深处的水循环，因为将含氢的材料循环到行星的内部中。最近发现，来自深地球的多个天然钻石夹杂物包含含水阶段，这令人信服地证明，深地球的水周期可能比最初认为的更深。这项研究将使用计算模型和实验的组合来评估被认为在地球下层的条件下稳定的液压相的稳定性和地球物理特性。尽管预计这些阶段将是次要的阶段，但在下层地幔中存储的潜力仍然相当大，因为它约占地球体积的56％。该项目将为早期职业科学家提供关键培训，他们将通过学习如何在主要本科机构的教学，研究和学生指导之间进行指导。 A complementary educational component of this project is to develop a virtual reality application that will help undergraduate geology students develop spatial reasoning skills, with a particular focus on fostering equity and inclusion for neurodiverse students with visual-spatial deficits.Phase D [MgSi2O4(OH)2] and phase H [MgSiO2(OH)2] are dense hydrous magnesium silicates (DHMSs) that are expected to play在下地幔的氢周期中的关键作用。重要的是，Fe-和Al-substitution对这些阶段的稳定性和特性具有深远的影响。实际上，相H形成了用D-Alooh和E-FeOOH形成的实心溶液，形成了潜在的连续液压储层，并稳定到核心壳边界。该项目将AB的初始计算与高压，高温振动光谱和单晶X射线衍射相结合，以评估Al，Fe-Bearing相位D和相H的中间组合物的地球物理特性，并探测阳离子替代如何影响压力串压的压力，从而影响了实质性的模型，并对其进行了实质性的影响。第一个原理计算将系统地评估阳离子替代如何影响这些阶段中压力依赖性的特性和氢化，从而为高压实验提供了理论框架。结合晶体学和光谱方法将在这些阶段内提供有关原子间力和氢的粘结环境的详细信息，这有助于解释为什么在极端压力和温度下这些阶段稳定。这一奖项反映了NSF的法定任务，并通过使用该基金会的知识优点和广泛的影响来评估NSF的法定任务。