Understanding the stability of superionic phases in Earth's inner core

The superionic state is a unique phase of matter where liquid-like mobility occurs within a solid crystalline lattice. This peculiar state was recently discovered in the Earth's inner core. Understanding the equilibration of this superionic phase with liquid solutions under core conditions is crucial for investigating the core's properties and evolution but remains a challenge. This talk presents a method for calculating the ab initio Gibbs free energy of the superionic states and the superionic-liquid phase diagrams for Fe-light element systems near the Earth's inner core boundary. We clarify the stability fields of superionic phases in hcp and bcc structures and show how the superionic state affects light element concentrations in the core, providing a quantitative approach to understanding superionic-liquid equilibrium in the core.