Hyperconnected amorphous oxide networks under compression.

Area of Science:

• Materials Science
• Solid State Chemistry
• Geophysics

Background:

• Irreversibly densified oxide glasses exhibit unexpected softening and plasticity, contradicting the typical rigidification upon densification.
• The atomic-level mechanisms governing these distinct mechanical responses in amorphous networks are not well understood.
• Understanding network entanglement and connectivity under high pressure is crucial for explaining these phenomena.

Purpose of the Study:

• To investigate the atomic-level changes in densified amorphous oxides under extreme deformation.
• To elucidate the relationship between network structure, entanglement, and mechanical properties.
• To explore the role of configurational diversity and hyperconnectivity in glass behavior.

Main Methods:

• Magnetic resonance spectroscopy was employed to measure densified amorphous oxides.
• Analysis focused on network entanglement, hyperconnectivity, and coordination of aluminum atoms.
• Investigated configurational diversity in amorphous aluminum oxide (Al2O3) and other complex oxide glasses.

Main Results:

• Evidence of enhanced network entanglement and hyperconnectivity was found in densified amorphous oxides.
• An increase in highly coordinated aluminum atoms and their spatial proximity indicated hyperconnectivity.
• Amorphous Al2O3 exhibited greater configurational diversity and reached hyperconnectivity at lower pressures compared to other oxide glasses.
• Configurational diversity was promoted by increasing field strength of non-network cations.

Conclusions:

• Enhanced connectivity, particularly hyperconnectivity at lower pressures, may promote network flexibility during deformation.
• This work provides a conceptual framework for controlling dual mechanical responses in glasses under stress.
• Findings guide the development of super-hard densified glasses and explain the weakening of hyperconnected glasses in planetary interiors.