High pressure electrides: a predictive chemical and physical theory

Area of Science:

• Materials Science
• Solid-State Physics
• Quantum Chemistry

Background:

• Electrides are crystalline phases where electrons act as anions in interstitial sites.
• High pressure can induce the formation of novel electride phases in various elements.

Purpose of the Study:

• To propose a unified theory for high pressure electrides (HPEs).
• To explain and predict the conditions under which elements form HPEs.
• To identify trends in HPE formation across the periodic table.

Main Methods:

• Developed a theory treating interstitial electrons as occupying quantized orbitals, forming an interstitial quasi-atom (ISQ).
• Utilized a He lattice model to simulate high-pressure compression of atoms and interstitial spaces.
• Analyzed the pressure-dependent energy shifts of atomic orbitals and ISQ levels.

Main Results:

• Proposed that HPEs form when atomic valence orbitals exceed ISQ energy levels under pressure.
• Orbital energy slopes with pressure (s > p > d) are crucial for predicting HPE formation.
• Predicted specific elements (Al, Mg, Si, Tl, In, Pb) likely to form HPEs below 500 GPa.

Conclusions:

• The interstitial quasi-atom model provides a framework for understanding HPE formation.
• Pressure-induced changes in orbital energies dictate the propensity for electride formation.
• The study offers predictions for new electride phases and their potential properties.