CAREER: Elasticity and Lattice Dynamics of Iron Alloys under Earth's Core Conditions

地核位于地球的中心，是地球最深处但却极具活力的区域。在过去的二十年里，地球物理学家在破译地核的成分组成、热结构和地震特征方面付出了巨大的努力。了解地核的性质和动力学可以大大提高我们理解磁场产生过程、地球深部热化学演化以及地球作为宜居行星的形成的能力。该学院早期职业发展（Career）项目旨在利用多尺度最先进的实验设施，研究铁合金在高压和高温条件下作为内核候选材料的弹性和晶格动力学。所提出的研究结果是一套新的基本矿物物理数据，包括密度、声速和铁合金在以前未知的压力-温度制度下的单晶弹性，这对我们进一步限制岩心的组成和动力学至关重要。实验结果将被整合到地核的综合矿物物理数据库中，促进与地震学、地球动力学和地球化学等姊妹学科的合作，最终增强我们对地球最深处的自然和动力学的深刻理解。此外，学生研究人员参与拟议的研究和开发高压矿物和材料科学的研究和教学设施将启动“管道”，帮助影响和吸引不同的学生群体，特别是传统上代表性不足的少数民族，进入地球科学，并建立多样化的地球科学劳动力。本课题旨在利用同步辐射x射线光谱技术，结合电阻和激光加热金刚石砧细胞技术，系统测量候选铁合金的高压-高温弹性和振动性能，以解决以下科学问题：(1)压力和温度如何影响铁合金在核心条件下的弹性和振动性能？(2)在铁芯条件下，候选轻元素对铁弹性的合金化效果如何？(3)接近岩心条件下的铁合金单晶弹性如何解释岩心地震各向异性和精细尺度地震？(4)最后，内核中可能有哪些较轻的合金成分，这对内核和行星的热化学演化意味着什么？综合教育和推广目标是在实验室和同步加速器设施中培养新一代独立的固体地球地球科学家，并通过在地球科学课程中实施“多砧压力机实验室”（MAPLab）教学模块，为K-16学生提供基于探究的学习机会和经验。该项目的成果将通过国家和国际会议、公开演讲和外联以及新闻媒介及时广泛传播。

Residing at the center of the Earth, the core is the innermost but extremely dynamic region of our planet. Over the last two decades, geophysicists have expended tremendous effort in deciphering the compositional makeup, thermal structure, and seismic features of the Earth's core. Understanding the nature and dynamics of the core can deeply enhance our abilities in understanding the magnetic field generation process, the thermo-chemical evolution of the Earth's deep interior, and the formation of the Earth as a habitable planet. This Faculty Early Career Development (CAREER) program aims to investigate the elasticity and lattice dynamics of iron alloys as candidates for the inner core under high pressure and temperature conditions of the core, using multiscale state-of-the-art experimental facilities. The outcome of the proposed research is a new set of fundamental mineral physics data on density, sound velocities, and single-crystal elasticity of iron alloys under previously uncharted pressure-temperature regimes, essential for us to provide further constraints on the core's composition and dynamics. The experimental results are to be integrated to a comprehensive mineral physics database for the core, cultivating collaborations with sister disciplines such as seismology, geodynamics and geochemistry, and ultimately enhancing our profound understanding of nature and dynamics of the Earth's deepest interior. Furthermore, the involvement of student researchers in the proposed research and the development of a research and teaching facility for high-pressure mineral and materials science will initiate the 'pipeline' that helps influence and attract diverse student population, particularly traditionally underrepresented minorities, into Earth science and build diverse geoscience workforce.This proposal aims to systematically measure high pressure-temperature elastic and vibrational properties of candidate iron alloys for the inner core, using synchrotron-based X-ray spectroscopies combined with resistively- and laser-heated diamond anvil cell techniques, so as to address the following scientific questions: (1) How do pressure and temperature affect the elastic and vibrational properties of iron alloys under core conditions? (2) What are the alloying effects of candidate light elements on the elasticity of iron under core conditions? (3) What are the single crystal elasticities of iron alloys approaching the core conditions, for the interpretation of the inner core's seismic anisotropy and fine-scale seismic? (4) Finally, what are the likely lighter alloying components in the inner core and what would that imply for the thermochemical evolution of the core and the planet? The integrated education and outreach objective is to train a new generation of independent solid Earth geoscientists in laboratory- and synchrotron-based facilities and to offer inquiry-base learning opportunities and experience to K-16 students through the implementation of a 'Multi-Anvil Press Laboratory' (MAPLab) teaching module to geosciences curricula. The results of the project will be widely disseminated on a timely manner through national and international meetings, public lectures and outreach, and news media.