5617 20220125202444.0 10.1038/s41467-022-27991-9 DOI SCART-2022-0023 Edmund, E. The Fe-FeSi phase diagram at Mercury’s core conditions 2022 Mercury’s metallic core is expected to have formed under highly reducing conditions, resulting in the presence of significant quantities of silicon alloyed to iron. Here we present the phase diagram of the Fe-FeSi system, reconstructed from in situ X-ray diffraction measurements at pressure and temperature conditions spanning over those expected for Mercury’s core, and ex situ chemical analysis of recovered samples. Under high pressure, we do not observe a miscibility gap between the cubic fcc and B2 structures, but rather the formation of a re-entrant bcc phase at temperatures close to melting. Upon melting, the investigated alloys are observed to evolve towards two distinct Fe-rich and Fe-poor liquid compositions at pressures below 35-38 GPa. The evolution of the phase diagram with pressure and temperature prescribes a range of possible core crystallization regimes, with strong dependence on the Si abundance of the core. 3PRODPLANINT/ 3PRODPLANINT/ 3PRODPLANINT NO Morard, G. Baron, M. A. Rivoldini, A. Yokoo, S. Boccato, S. Hirose, K. Pakhomova, A. Antonangeli, D. Nature Communications 13 2022 1 attilio.rivoldini@observatoire.be 1341945 http://publi2-as.oma.be/record/5617/files/Edmund2022ut81.pdf 2252038 http://publi2-as.oma.be/record/5617/files/Edmund2022ut00.pdf 2927 http://publi2-as.oma.be/record/5617/files/Edmund2022ut00.jpg?subformat=icon-180 icon-180 2963 http://publi2-as.oma.be/record/5617/files/Edmund2022ut00.gif?subformat=icon icon 5541 http://publi2-as.oma.be/record/5617/files/Edmund2022ut81.gif?subformat=icon icon 7366 http://publi2-as.oma.be/record/5617/files/Edmund2022ut81.jpg?subformat=icon-180 icon-180 published in REFERD