Pressure-induced structural change of liquid silicon

Area of Science:

• Materials Science
• Condensed Matter Physics
• High-Pressure Science

Background:

• Understanding the behavior of silicon under extreme conditions is crucial for materials science.
• Previous studies on liquid silicon structure at high pressures have yielded complex and sometimes contradictory results.
• Network liquids with isotropic bonding present unique challenges in predicting their response to pressure.

Purpose of the Study:

• To investigate the structural changes in liquid silicon under high pressure.
• To determine the pressure-induced transformation points and associated structural modifications.
• To elucidate the nature of bonding and local structure in dense liquid silicon.

Main Methods:

• High-pressure and high-temperature X-ray diffraction measurements.
• Analysis of radial distribution functions and coordination numbers.
• In-situ structural characterization under pressures up to 14 GPa.

Main Results:

• Liquid silicon exhibits volume contraction up to 8 GPa with minimal local structure changes.
• A transformation to a denser structure occurs between 8 and 14 GPa.
• Anomalous expansion of nearest-neighbor distances (1.6%) and increased coordination number observed during this transformation.

Conclusions:

• Drastic pressure-induced structural changes are possible in three-dimensional-network liquids.
• The isotropic bonding nature of silicon contributes to its unique high-pressure behavior.
• Findings challenge conventional models of liquid structural response to pressure.