Phase relations and physical properties of iron-oxygen compounds at multimegabar pressures and high temperatures

Fe-O系化合物的结构、性质以及高温高压行为一直备受争议，尽管有很长的研究历史，但仍然充满了惊喜。在过去的十年里，人们发现了几种化学计量未知的高压氧化铁。这些材料对于地球科学(和行星科学)来说是非常重要的，因为它们是地球吸积过程中的潜在相，是现代地幔的可能成分，对于控制地幔、核地幔边界和地核中的氧逸度是非常重要的。此外，新型铁氧化物的电子和磁性对现代固态物理、化学、材料科学甚至工业(作为开关电子学和存储器中的元件)都非常感兴趣。铁氧化物将在200 Gpa以上的压力和高达3500 K的温度下合成，并在激光加热的金刚石压腔(DAC)中进行现场研究，采用一系列先进的补充技术：X射线衍射(X射线衍射)、穆斯堡尔和拉曼光谱(如果适用的话X射线吸收光谱和电阻率测量)和理论计算。该项目的方法学目标是将单晶衍射研究扩展到200 Gpa以上。将特别关注FeO、Fe3O4、Fe2O3、Fe4O5、Fe5O6、Fe5O7、Fe7O9和FeO2的研究。该项目的最终目标是建立覆盖整个地幔和核心重要部分的Fe-O系统的压力-温度-组成(P-T-X)相图；分析压力-温度诱导的Fe-O化合物的转变如何影响地球内部的地球化学过程；揭示不同铁氧化物的结构、化学键和性质之间的关系；以及制定控制过渡金属氧化物在极端条件下行为的晶体化学原理。

The structures, properties and high-pressure and high-temperature behavior of compounds in the Fe–O system remain controversial and full of surprises despite a long history of research. Over the last decade several high-pressure iron oxides with hitherto unknown stoichiometries were discovered. These materials are very important for the geosciences (and planetary sciences) as potential phases during the Earth’s accretion, as possible components of present day mantle, and for controlling oxygen fugacity in the mantle, core mantle boundary, and in the core. Moreover, novel iron oxides, their electronic and magnetic properties are of great interest for modern solid state physics, chemistry, material sciences, and even for in the industry (as elements in switching electronics and memories).Iron oxides will be synthesized at pressures over 200 GPa and temperatures up to 3500 K and studied in situ in laser-heated diamond anvil cells (DACs) employing a range of advanced complementary techniques: X-ray diffraction (XRD), Mössbauer and Raman spectroscopy (and when applicable X-ray absorption spectroscopy and electrical resistivity measurements) and theoretical calculations. Methodological aim of the project is to extend single-crystal diffraction studies to over 200 GPa. Particular attention will be paid on studies of FeO, Fe3O4, Fe2O3, Fe4O5, Fe5O6, Fe5O7, Fe7O9, and FeO2. The ultimate goals of the project are to construct pressure-temperature-composition (P–T–X) phase diagram of Fe–O system at conditions covering entire Earth mantle and significant part of the core; analyze how pressure-temperature induced transformations in Fe–O compounds may affect geochemical processes in the Earth’s interior; reveal relations between structure, chemical bonding, and properties of different iron oxides; and formulate crystal chemical principals governing behavior of transition metal oxides at extreme conditions.