Revisiting local structural changes in GeO₂ glass at high pressure.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Geochemistry

Background:

• Understanding pressure-induced structural changes in network-forming glasses like GeO2 is crucial for both fundamental science and industrial applications.
• Polyamorphism, the ability of a material to exist in multiple distinct structural forms at different pressures, is a key phenomenon in glass science.

Purpose of the Study:

• To investigate the local structural transformations in GeO2 glass under high pressure up to 54 GPa.
• To identify and characterize the polyamorphic transitions occurring in GeO2 glass using advanced spectroscopic techniques.

Main Methods:

• Utilized X-ray absorption fine structure (XAFS) spectroscopy to probe local atomic environments.
• Employed a diamond anvil cell for high-pressure generation and a polycapillary half-lens for efficient X-ray focusing.
• Performed XAFS structure refinement to analyze spectral data and determine structural parameters.

Main Results:

• Identified three distinct polyamorphic transitions in GeO2 glass within the studied pressure range.
• Observed progressive changes in Ge-O distance and bond disorder, indicative of tetrahedral-to-octahedral coordination shifts.
• Provided evidence for ultrahigh-pressure polyamorphism with coordination numbers exceeding 6, along with cooperative structural modifications in more distant shells.

Conclusions:

• The study provides a unified local structural picture of polyamorphic transitions and densification in GeO2 glass.
• The findings enhance the understanding of how network-forming glasses respond to extreme pressure conditions.
• This research contributes to the broader knowledge of phase transitions in amorphous materials.