Abstract
Recent studies suggest that H is an important light element in the Earth’s core for its high cosmochemical abundance and strong affinity to Fe under core-formation conditions. Thus, constraining the light element contents in the core requires knowledge on the distribution of H between the liquid outer core and solid inner core. Here we investigate the chemical equilibrium of H at the inner-core boundary (ICB) by calculating the chemical potential of H in solid and liquid Fe-H alloys, respectively, using first-principles molecular dynamic simulations in conjunction with the particle insertion and neural network methods. We find that H partitions preferentially into the outer core and provides a major contribution to the density jump across the ICB boundary. Combining geophysical constraints, mineral physics data, and chemical equilibrium at the ICB, we evaluated light element abundances in the outer and inner cores simultaneously. Our results suggest H and Si are the preferred light elements in the core, implying a relatively reduced environment during the Earth’s accretion and core-formation processes.