Decoding entangled transitions: Polyamorphism and stressed rigidity.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Chemistry

Background:

• Polyamorphism, the ability of a material to exist in multiple distinct amorphous phases, is observed in various systems.
• Chalcogenide glasses, like Germanium-Selenium (Ge-Se) glasses, exhibit unique elastic phase transitions and network connectivity changes.
• Topological constraint theory provides a framework for understanding the rigidity of amorphous networks.

Purpose of the Study:

• To investigate the relationship between polyamorphism and network rigidity in Ge-Se glasses under varying thermodynamic conditions.
• To extend the concept of rigidity to densified glasses and high-pressure phases.
• To validate simulation models against experimental data for GeSe4 under pressure.

Main Methods:

• First-principles molecular dynamics simulations were employed to model the structural behavior of Ge-Se glasses.
• Experimental data across a broad pressure range were used to validate the simulation models.
• Topological constraint theory was applied to analyze network connectivity and rigidity.

Main Results:

• The onset of polyamorphism in Ge-Se glasses strongly correlates with constraint density, indicating network rigidity.
• Voids and cavities within the glass structure collapse at low pressures.
• Higher coordinated species and stiffening bonding angles contribute to stressed rigidity at high pressures.

Conclusions:

• Constraint density is a key factor in the onset of polyamorphism in Ge-Se glasses.
• The study provides insights into the structural evolution of chalcogenide glasses under pressure.
• The findings can be generalized to other compositions within the Ge-Se binary system.