Predicted stable electrides in Mg-Al systems under high pressure

Area of Science:

• Materials Science
• Solid State Chemistry
• Computational Materials Science

Background:

• Magnesium (Mg) and aluminum (Al), adjacent light metals, exhibit limited stable compound formation under ambient conditions.
• Understanding Mg-Al phase diagrams and structures under extreme conditions is crucial for materials science.

Purpose of the Study:

• To systematically explore the Mg-Al compositional space at high pressures (up to 100 GPa).
• To identify novel thermodynamically stable Mg-Al stoichiometries and characterize their electronic properties.

Main Methods:

• Utilized evolutionary ab initio structural prediction methods.
• Conducted comprehensive computational searches across the entire Mg-Al compositional landscape.
• Analyzed electronic structures to determine compound stability and properties.

Main Results:

• Predicted three new thermodynamically stable Mg-Al compounds: Mg₃Al, MgAl, and MgAl₃, under specific high-pressure regimes.
• Identified these compounds as novel electrides, characterized by excess electrons confined in interstitial voids.
• Attributed the electride nature to the high-pressure induced overlap of 3p orbitals in neighboring Al atoms.

Conclusions:

• The study reveals previously unknown stable Mg-Al compounds and their electride nature under high pressure.
• Provides a theoretical foundation for experimental synthesis and characterization of these novel Mg-Al materials.
• Advances the understanding of materials chemistry and electron behavior in high-pressure environments.