地球深部条件下FeO中铁的相变与自旋态
Phase transitions and spin-state of iron in FeO at the conditions of Earth's deep interior
AI总结：
本文利用X射线衍射、X射线发射光谱与DFT+DMFT方法，研究FeO在高达140 GPa和2100 K条件下的电子结构、自旋态和晶体结构，发现其在核幔边界条件下存在金属性高自旋态高压相，并伴随异常压缩行为和体弹模量显著变化，对理解地球深部地球物理与地球化学性质具有重要意义。
摘要：
含铁氧化物经历一系列压力诱导的电子、自旋和结构转变，这些转变可在地幔和外核中引起地震异常和动力学不稳定性。我们采用X射线衍射和X射线发射光谱，结合最先进的密度泛函加动力学平均场理论（DFT+DMFT），来表征方铁矿（Fe$_{1-x}$O）——地球内部的一种基本氧化物组分——在高达140 GPa和2100 K的高压高温条件下的电子结构、自旋态以及晶体结构性质。我们发现FeO在压力下表现出复杂的多形性，具有与电子自旋和晶体学相变相关的异常压缩行为，并导致体弹模量的显著变化。我们的结果揭示了一个高压相的存在，其特征是在大约地球核幔边界的压力-温度条件下铁处于金属性高自旋态。在地幔底部附近存在高自旋金属铁可以显著影响地球深部的地球物理和地球化学性质。
英文摘要：
Iron-bearing oxides undergo a series of pressure-induced electronic, spin and structural transitions that can cause seismic anomalies and dynamic instabilities in Earth's mantle and outer core. We employ x-ray diffraction and x-ray emission spectroscopy along with state-of-the-art density functional plus dynamical mean-field theory (DFT+DMFT) to characterize the electronic structure and spin states, and crystal-structural properties of wüstite (Fe$_{1-x}$O) -- a basic oxide component of Earth's interior -- at high pressure-temperature conditions up to 140 GPa and 2100 K. We find that FeO exhibits complex polymorphism under pressure, with abnormal compression behavior associated with electron-spin and crystallographic phase transitions, and resulting in a substantial change of bulk modulus. Our results reveal the existence of a high-pressure phase characterized by a metallic high-spin state of iron at about the pressure-temperature conditions of Earth's core-mantle boundary. The presence of high-spin metallic iron near the base of the mantle can significantly influence the geophysical and geochemical properties of Earth's deep interior.
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