Growing length scale accompanying vitrification: A perspective based on nonsingular density fluctuations

Area of Science:

• Condensed Matter Physics
• Materials Science
• Statistical Mechanics

Background:

• Vitrification, the process of forming a glass, involves a growing length scale.
• Existing models often rely on complex thermodynamic arguments to explain this phenomenon.

Purpose of the Study:

• To introduce a new model for vitrification that describes the growing length scale.
• To explain the mechanism behind this length scale divergence without complex thermodynamics.

Main Methods:

• Introduced a model based on
• Defined
• Assumed that in subsystems with density above a threshold (ρc), particle rearrangements are suppressed due to steric constraints, forming
• Predicted the divergence of the characteristic cluster length scale (ξ) with compression (increasing density ρ) and cooling (decreasing temperature T).

Main Results:

• The model predicts a diverging length scale ξ∼(ρc−ρ)−2/d with increasing density and ξ∼(T−Tc)−2/d with decreasing temperature, where d is spatial dimensionality.
• The predicted exponent for the diverging length scale matches existing theoretical models and experimental observations.
• The proposed mechanism for length scale divergence is distinct from thermodynamic anomalies associated with phase transitions.

Conclusions:

• The model provides a simpler, non-thermodynamic explanation for the growing length scale during vitrification.
• The concept of glassy clusters and steric constraints offers a new perspective on the cooperative nature of structural relaxation in supercooled liquids.