Quasimolecules in Compressed Lithium

Area of Science:

• Materials Science
• Solid-State Physics
• Quantum Chemistry

Background:

• High pressure can induce unique electronic structures in materials, leading to the formation of electrides.
• Electrides feature delocalized valence electrons in interstitial regions, often resulting in semiconducting or insulating properties.
• Interstitial quasiatoms (ISQ) are theoretical constructs within electrides, potentially exhibiting atomic-like chemical behavior.

Purpose of the Study:

• To investigate the chemical nature of interstitial quasiatoms (ISQ) in high-pressure electrides.
• To determine if ISQ can form covalent bonds, analogous to atoms.
• To explain the insulating behavior of the high-pressure semiconducting lithium phase (oC40, Aba2) using the quasimolecule concept.

Main Methods:

• Theoretical evaluation of electron density.
• Analysis of the electron localization function (ELF).
• Wannier orbital analysis and bond index calculations.

Main Results:

• Evidence for covalently bonded ISQ pairs was found in the high-pressure semiconducting Li phase.
• The quasimolecule concept successfully explains the insulating behavior.
• The findings complement existing physical models focusing on crystal symmetry.

Conclusions:

• Interstitial quasiatoms in high-pressure electrides can form covalent bonds, acting as quasimolecules.
• The quasimolecule model offers a simplified chemical perspective on the electronic properties of these materials.
• This research bridges chemical intuition and physical understanding of exotic high-pressure phases.