Gallium and indium under high pressure

Area of Science:

• Condensed matter physics
• Materials science
• Computational physics

Background:

• Gallium (Ga) and Indium (In) are Group-III elements known for unusual open ground-state crystal structures.
• Experimental data shows Ga transforms to a close-packed structure under high pressure, but In has not exhibited this behavior.

Purpose of the Study:

• To explain the difference in high-pressure structural behavior between Ga and In.
• To predict the high-pressure phase transitions of In.
• To identify the underlying mechanism governing structure determination in Group-III elements.

Main Methods:

• First-principles calculations were employed to investigate the structural properties of Ga and In under pressure.
• Analysis focused on the electronic structure, specifically the degree of s-p mixing of valence orbitals.

Main Results:

• The study provides a simple explanation for the differing high-pressure behaviors of Ga and In.
• A previously undiscovered transition of In to a close-packed structure at extreme pressures is predicted.
• The degree of s-p mixing in valence orbitals is identified as the key mechanism determining the crystal structure.

Conclusions:

• Group-III elements significantly deviate from the standard corresponding-state rule.
• The electronic structure, particularly s-p orbital mixing, is crucial for understanding pressure-induced phase transitions in these elements.
• Further experimental investigation into the high-pressure behavior of In is warranted.