Electronic Spin Transition of Iron in the Earth's Lower Mantle

穿过地球的地震波提供了关于地球的基本知识？室内。地球的矿物学模型表明，下地幔是深度670 ~ 2900 km（压力~23 ~ 140 GPa，温度约1800 ~ 4000 K）的体积最大的层，由约30%的铁方石矿[(Mg,Fe)O]和70%的硅酸盐钙钛矿（含少量铝[Al-(Mg,Fe,)SiO3]）组成，此外还有少量的硅酸钙钛矿（CaSiO3）。硅酸盐钙钛矿在核幔边界上方转变为后钙钛矿结构。地球的性质？因此，下地幔被认为是由这种矿物组合控制的，其中铁是最丰富的过渡金属，可以在高压和高温下进行电子自旋和价态转变，并可能改变这些矿物的性质。本研究旨在研究铁镁长石、钙钛矿和后钙钛矿等下地幔矿物组合中铁的电子自旋跃迁性质，重点研究影响下地幔化学和物理动力学的相关性质。这些实验将结合实验室和基于同步加速器的设备以及高压-高温金刚石砧单元，探索与下地幔结构和地球动力学建模最相关的物理特性，包括状态热方程、变形和强度、声速和传输特性。这些研究以自旋转变为重点，旨在了解不同压力-温度-组成条件下下地幔矿物的性质，在层析成像和地球物理模型快速发展的今天，为了解下地幔的状态提供直接的矿物物理结果。预期的结果是地球物理学和地球动力学的基础，将为下地幔的地震、矿物学和地球动力学行为的令人满意的建模提供新的信息方面。该项目还将开发新的高压技术，这将使广泛的深地幔群落的研究人员和学生受益。

Seismic waves traveling through the Earth have provided fundamental knowledge of the Earth?s interior. Mineralogical models of the planet indicate that the lower mantle, the most voluminous layer extending from 670 km to 2900 km in depth (~23 GPa to 140 GPa in pressures and approximately 1800 K to 4000 K in temperatures), consists of approximately 30% ferropericlase [(Mg,Fe)O] and 70% silicate perovskite containing minor amounts of aluminum [Al-(Mg,Fe,)SiO3], in addition to a small amount of calcium silicate perovskite (CaSiO3). Silicate perovskite transforms to a post-perovskite structure just above the core-mantle boundary. The properties of the Earth?s lower mantle are thus thought to be governed by this mineral assemblage, in which iron is the most abundant transition metal that can undergo electronic spin and valence transitions under high pressures and temperatures, and may alter the properties of these minerals.This proposal aims to study the nature of electronic spin transitions of iron in the lower mantle mineral assemblage, including ferropericlase, perovskite, and post-perovskite, with emphasis on associated properties influencing the chemical and physical dynamics of the lower mantle. Using a combination of laboratory and synchrotron-based facilities with high pressure-temperature diamond anvil cells, these experiments will probe physical properties most relevant to modeling the structure and geodynamics of the lower mantle including thermal equations of state, deformation and strength, sound velocities, and transport properties. With an emphasis on the spin transitions, these studies aim broadly to understand properties of the lower-mantle minerals at various pressure-temperature-composition conditions, providing direct mineral physics results for input into understanding the state of the lower-mantle at a time when tomographic images and geophysical models of the lower mantle are rapidly advancing. The expected results are fundamental to geophysics and geodynamics of the Earth and will provide new aspects of information to modeling satisfactorily the seismic, mineralogical, and geodynamic behavior of the lower mantle. The project will also develop new high-pressure techniques that will benefit researchers and students in the broad deep-mantle communities.