Pressure-Induced Flat Bands and Electride Behavior in SC Mg

Abstract

The high-pressure phase diagram of Magnesium (Mg) has attracted significant attention due to its relevance as a constituent of Earth’s inner core (IC), where it profoundly influences physical behavior and properties under extreme conditions. A recent study has revealed multiple crystal structure transitions in Mg, including the emergence of non-close-packed phases at extreme pressures. We investigate the electronic structure of simple cubic (SC) Mg under extreme pressure using Density Functional Theory (DFT) calculations. At 1320 GPa, our analysis shows that charge density accumulates at the center of the unit cell, increasing as pressure rises. The electron localization function (ELF) reveals that electrons are not just confined to atomic sites but also extend into interstitial regions, suggesting a shift in bonding character driven by p-d-orbital contributions. Additionally, the electronic band structure and density of states (DOS) confirm that Mg remains metallic at this pressure. A distinct flat band appears along the X-M path in the Brillouin zone, indicating enhanced electronic correlations that could influence the transport properties of Mg. These results highlight how extreme compression reshapes electronic interactions, potentially leading to novel high-pressure phenomena.