Pressure-induced redox reversal of iron and the distribution of elements in deep Earth

Through large-scale, first-principles calculations, we show that iron reacts with p-block elements under pressures ranging from ambient to those of Earth’s core. More importantly, it undergoes a reversal in redox character, shifting from an electron donor/reducing agent to an electron acceptor/oxidizing agent, thereby oxidizing many p-block elements. This reversal alters the stoichiometry, bonding nature and strength, structures, and properties of iron compounds formed under deep-Earth conditions. As a result, p-block elements traditionally labeled lithophile or chalcophile are transformed into highly siderophile species. The strength of their chemical bonds with iron shows an inverse correlation with their observed depletion in the silicate Earth. Silicon also exhibits a unique bonding anomaly with iron, suggesting it can be readily incorporated into Earth’s core.