The effect of Ni on the formation and structure of Earth’s inner core

The Fe-Ni alloy is believed to be the main component of Earth's core. Yet, Ni’s effects on the inner core’s structure and formation process are often disregarded due to its similarity to Fe. Using ab initio simulations, we find that Ni can stabilize bcc structures and accelerate Fe’s crystallization at high temperatures and inner core pressures. We computed the Gibbs free energy and phase diagram for liquid and solid solutions of Fe-Ni alloys under inner core conditions, providing new insights into the possible structure of the inner core. The results offer new constraints for the study of the core’s composition and formation.