Densified network glasses and liquids with thermodynamically reversible and structurally adaptive behaviour

Area of Science:

• Materials Science
• Condensed Matter Physics
• Chemical Engineering

Background:

• Glasses form from liquids that avoid crystallization upon cooling, exhibiting increased viscosity and solid-like behavior.
• Off-equilibrium dynamics lead to hysteresis loops during cooling/heating cycles across the glass transition temperature.

Purpose of the Study:

• To investigate the behavior of densified glass-forming liquids under cooling/heating cycles.
• To explore the phenomenon of thermally reversible glass transitions and their underlying mechanisms.

Main Methods:

• Molecular dynamics simulations were employed to model densified glass-forming liquids undergoing thermal cycles.
• Analysis of atomic network topology and dynamic behavior was conducted to understand structural changes.

Main Results:

• A finite pressure interval was identified where glasses exhibit 'thermally reversible' character with optimal recovery.
• Increased pressure induced larger bond-angle excursions in the atomic network, adapting to stress.
• Adaptive liquids showed substantially reduced structural relaxation times, driving the reversible glass transition.

Conclusions:

• The findings support the concept of stress-free (Maxwell isostatic) rigidity in disordered molecular systems.
• The study reveals new possibilities for topological engineering in complex materials by controlling glass transition reversibility.