5879 20221105150539.0 10.1029/2022JB025117 DOI SCART-2022-0109 Morard, Guillaume Structural and Electronic Transitions in Liquid FeO Under High Pressure 2022 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. 3PRODPLANINT/ 3PRODPLANINT/ 3PRODPLANINT NO Antonangeli, Daniele Bouchet, Johann Rivoldini, Attilio Boccato, Silvia Miozzi, Francesca Boulard, Eglantine Bureau, Hélène Mezouar, Mohamed Prescher, Clemens Chariton, Stella Greenberg, Eran Journal of Geophysical Research: Solid Earth 127 2022 11 attilio.rivoldini@observatoire.be 1796688 http://publi2-as.oma.be/record/5879/files/Morard2022aa00.pdf 21022 http://publi2-as.oma.be/record/5879/files/Morard2022aa00.gif?subformat=icon icon 23522 http://publi2-as.oma.be/record/5879/files/Morard2022aa00.jpg?subformat=icon-180 icon-180 published in REFERD