Morard, Guillaume ; Antonangeli, Daniele ; Bouchet, Johann ; Rivoldini, Attilio ; Boccato, Silvia ; Miozzi, Francesca ; Boulard, Eglantine ; Bureau, Hélène ; Mezouar, Mohamed ; Prescher, Clemens ; Chariton, Stella ; Greenberg, Eran

published in Journal of Geophysical Research: Solid Earth, 127 issue 11 (2022)

Abstract: 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.

DOI: 10.1029/2022JB025117
Funding: 3PRODPLANINT/3PRODPLANINT/3PRODPLANINT