Morard Guillaume, Antonangeli Daniele, Bouchet Johann, Rivoldini Attilio, Boccato Silvia, Miozzi Francesca, Boulard Eglantine, Bureau Hélène, Mezouar Mohamed, Prescher Clemens, Chariton Stella, Greenberg Eran
CNRS IRD IFSTTAR ISTerre Université Grenoble Alpes Université Savoie Mont Blanc Grenoble France.
Muséum National d'Histoire Naturelle UMR CNRS 7590 Institut de Minéralogie de Physique des Matériaux et de Cosmochimie IMPMC Sorbonne Université Paris France.
J Geophys Res Solid Earth. 2022 Nov;127(11):e2022JB025117. doi: 10.1029/2022JB025117. Epub 2022 Nov 5.
FeO represents an important end-member for planetary interiors mineralogy. However, its properties in the liquid state under high pressure are poorly constrained. Here, in situ high-pressure and high-temperature X-ray diffraction experiments, ab initio simulations, and thermodynamic calculations are combined to study the local structure and density evolution of liquid FeO under extreme conditions. Our results highlight a strong shortening of the Fe-Fe distance, particularly pronounced between ambient pressure and ∼40 GPa, possibly related with the insulator to metal transition occurring in solid FeO over a similar pressure range. Liquid density is smoothly evolving between 60 and 150 GPa from values calculated for magnetic liquid to those calculated for non-magnetic liquid, compatibly with a continuous spin crossover in liquid FeO. The present findings support the potential decorrelation between insulator/metal transition and the high-spin to low-spin continuous transition, and relate the changes in the microscopic structure with macroscopic properties, such as the closure of the Fe-FeO miscibility gap. Finally, these results are used to construct a parameterized thermal equation of state for liquid FeO providing densities up to pressure and temperature conditions expected at the Earth's core-mantle boundary.
氧化亚铁是行星内部矿物学的一种重要端元。然而，其在高压液态下的性质却知之甚少。在此，结合原位高压高温X射线衍射实验、从头算模拟和热力学计算，研究了极端条件下液态氧化亚铁的局部结构和密度演化。我们的结果突出显示了铁-铁间距的显著缩短，在常压至约40吉帕之间尤为明显，这可能与固态氧化亚铁在类似压力范围内发生的绝缘体到金属的转变有关。在60至150吉帕之间，液态密度从磁性液体计算值平滑地演变为非磁性液体计算值，这与液态氧化亚铁中连续的自旋交叉相一致。目前的研究结果支持了绝缘体/金属转变与高自旋到低自旋连续转变之间可能存在的解耦，并将微观结构的变化与宏观性质联系起来，比如铁-氧化亚铁混溶间隙的闭合。最后，这些结果被用于构建液态氧化亚铁的参数化热状态方程，该方程能给出直至地核-地幔边界预期压力和温度条件下的密度。
