CAREER: Investigations on the elastic and vibrational properties of mantle silicates and oxides

对地球深部矿物学和化学成分的推断取决于将实验室测量的候选相的准确性质与地球物理和地球化学观测进行比较，因为我们直接对地球深部进行采样的能力受到严重限制。这个CAREER奖使用国家同步加速器设施研究铁和铝对下地幔硅酸盐和氧化物的弹性和振动性质的影响。在PI的指导下，学生将使用微x射线衍射和核共振非弹性x射线散射的同步加速器方法，在未知的压力-温度条件下获得地幔相的状态方程。 通常情况下，很少有学生能够在这些设施中体验研究项目，部分原因是有限的可达性和空间限制。在该项目的倡议下，我们将通过在同步加速器上建立现有的远程基础设施来创建虚拟光束线。加州理工学院的夏季本科生研究奖学金（SURF）计划向学生介绍在加州理工学院和喷气推进实验室经验丰富的研究导师的指导下进行研究。来自全国各地的本科生在夏天参加为期10周的SURF计划。在计划结束时，他们提交了一份技术论文，并在SURF研讨会日，一个模仿专业技术会议的研讨会上做口头报告。 拟议的研究议程及其虚拟光束线提供了一个独特的机会，为扩展阵列的本科生和研究生的指导下PI应用国家的最先进的实验技术在多尺度设施，并将其结果应用于地球物理现象。为了了解最近观测到的地震复杂性的起源，需要对候选的下地幔物质进行新的和更精确的测量，这是现代跨学科研究的一个活跃领域。通常，地球深部的模型是通过将矿物特性外推到相关的压力-温度条件下，并将其与地震学确定的压缩波和剪切波速度和密度进行比较来制作的。然而，由于实验的挑战，深地幔物质的一些性质仍然是未知的。为了克服这些障碍，本科生和研究生将使用已建立的同步加速器方法与金刚石砧室和激光加热技术相结合，以获得相关条件下地幔硅酸盐和氧化物的状态方程。与密度确定从X射线衍射这些材料，总的压缩和剪切波速度，以及绝热体模量和剪切模量，将确定从测量的部分声子态密度。通过创建一个虚拟光束线，以提供远程访问拟议的同步加速器实验，更多的本科生和研究生在加州理工学院将有机会获得同步加速器实验。学生们将在科学期刊上发表他们的研究结果，并在国家会议上介绍他们的发现。 获得的数据将允许评价铁和铝对以前未探索的压力-温度部门中这些材料的声速和弹性的影响，并将限制地球动力学模拟以及观察到的地震横向变化是否是由于化学来源。

Inferences of the mineralogy and chemical composition of Earth's deep interior depend on comparing accurate laboratory-measured properties of candidate phases with geophysical and geochemical observations, because our ability to directly sample the deep Earth is severely limited. This CAREER award investigates the effect of iron and aluminum on the elastic and vibrational properties of lower mantle silicates and oxides using national synchrotron facilities. Under the mentorship of the PI, students will use established synchrotron methods of micro x-ray diffraction and nuclear resonant inelastic x-ray scattering to obtain equations of state for mantle phases at unchartered pressure-temperature conditions. Typically, few students are able to experience research projects at such facilities due in part to limited accessibility and space constraints. Under the initiatives of this project, we will create a virtual beam-line by building on existing remote infrastructure at the synchrotron. Caltech's Summer Undergraduate Research Fellowships (SURF) program introduces students to research under the guidance of experienced research mentors at Caltech and the Jet Propulsion Laboratory. Undergraduate students from all over the country participate in a 10-week long SURF program over the summer. At the conclusion of the program, they submit a technical paper and give an oral presentation at SURF Seminar Day, a symposium modeled on a professional technical meeting. The proposed research agenda with its virtual beam-line offers a unique opportunity for an extended array of undergraduate and graduate students under the mentorship of the PI to apply state-of-the-art experimental techniques at multi-scale facilities and apply their results to geophysical phenomena. The effort to understand the origin of recently observed seismic complexities requires new and more accurate measurements of candidate lower mantle materials and is an active area of modern cross-disciplinary research. Typically, models of the deep Earth have been made by extrapolating mineral properties to relevant pressure-temperature conditions and comparing them with seismological determined compressional- and shear-wave velocities and density. However, several properties of deep mantle materials remain widely unknown due to experimental challenges. In an effort to overcome these obstacles, undergraduate and graduate students will use established synchrotron methods engaged with diamond anvil cells and laser heating technology to obtain equations of state for mantle silicates and oxides under relevant conditions. With the density determined from x-ray diffraction for these materials, the aggregate compressional and shear wave velocities, as well as the adiabatic bulk and shear moduli, will be determined from the measured partial phonon density of states. By creating a virtual beam-line to provide remote access to the proposed synchrotron experiments, more undergraduate and graduate students at Caltech will have access to synchrotron experiments. The students will publish their results in scientific journals and present their findings at national meetings. The data obtained will permit the evaluation of the effects of iron and aluminum on the sound velocities and elasticity of these materials in a previously unexplored pressure-temperatures sector and will put constraints on geodynamic simulations and whether observed seismological lateral variations are due to a chemical origin.