Intermediate-range order in permanently densified GeO2 glass

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid-State Chemistry

Background:

• Germanium dioxide (GeO2) glass is a key material in optics and photonics.
• Understanding the structural evolution of GeO2 glass under densification is crucial for tailoring its properties.
• Intermediate range order (IRO) describes structural correlations beyond nearest neighbors in amorphous materials.

Purpose of the Study:

• To investigate the structural changes in densified GeO2 glass.
• To determine the role of partial structure factors in the observed densification effects.
• To elucidate the atomic-scale mechanisms responsible for the reduction in the length scale of IRO.

Main Methods:

• Neutron diffraction measurements were performed on densified GeO2 glass.
• X-ray diffraction measurements were conducted on the same samples.
• Difference structure factors were calculated by combining neutron and x-ray data to isolate partial structure factors.

Main Results:

• Densification of GeO2 glass leads to a significant reduction in the length scale of the intermediate range order (IRO).
• Analysis of difference structure factors revealed that Ge-Ge correlations are most affected by densification, while O-O correlations are least affected.
• The reduction in IRO length scale is attributed to a decrease in next-nearest neighbor Ge-O and O-O distances.

Conclusions:

• The structural modifications in densified GeO2 glass involve rotations around Ge-O-Ge bonds and distortions of GeO4 tetrahedra.
• These atomic rearrangements lead to a more compact glass structure with reduced IRO.
• The findings provide insights into the structure-property relationships of amorphous germanium dioxide under pressure.