PBE-GGA Predicts the B8$\leftrightarrow$B2 Phase Boundary of FeO at Earth's Core Conditions

Abstract

FeO is a crucial phase of the Earth's core, and its thermodynamic properties are essential to developing more accurate core models. It is also a notorious correlated insulator in the NaCl-type (B1) phase at ambient conditions. It undergoes two polymorphic transitions at 300 K before it becomes metallic in the NiAs-type (B8) structure at $\sim$100 GPa. Although its phase diagram is not fully mapped, it is well established that the B8 phase transforms to the CsCl-type (B2) phase at core pressures and temperatures. Here we report a successful \textit{ab initio} calculation of the B8$\leftrightarrow$B2 phase boundary in FeO at Earth's core pressures. We show that fully anharmonic free energies computed with the PBE-GGA + Mermin functional reproduce the experimental phase boundary within uncertainties at $P>240$ GPa, including the largely negative Clapeyron slope of $-52\pm 5$ MPa/K. This study validates the applicability of a standard DFT functional to FeO under Earth's core conditions and demonstrates the theoretical framework that enables complex predictive studies of this region.

References in corpus (6)

• Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
• Entropy driven stabilization of energetically unstable crystal structures explained from first principles theory
• Orbital Selective Pressure-Driven Metal-Insulator Transition in FeO from Dynamical Mean-Field Theory
• Metal-ligand interplay in strongly-correlated oxides: a parametrized phase diagram for pressure induced spin transitions
• $\text{Ab initio}$ anharmonic thermodynamic properties of cubic CaSiO${}_3$ perovskite
• Anharmonic thermodynamic properties and phase boundary across the post-perovskite transition in MgSiO${}_3$

Cited by in corpus (3)

• Melting Temperature of Iron Under the Earth's Inner Core Condition from Deep Machine Learning
• Beyond Gaussian fluctuations of quantum anharmonic nuclei
• A Validated Low-to-Intermediate Mass Planetary Interior Structure Model and New Mass-Radius Relations