Macroscopic Illusion and Microscopic Reality of Glass Formation Paths: Cooling vs Compression

Area of Science:

• Condensed matter physics
• Materials science
• Chemical physics

Background:

• Glass-forming liquids exhibit complex dynamics, particularly dynamical slowdown near the glass transition.
• Understanding the microscopic mechanisms governing this slowdown is crucial for materials science and condensed matter physics.

Purpose of the Study:

• To investigate the microscopic routes of dynamical slowdown in glass-forming liquids under cooling and compression.
• To identify discrepancies between dynamical landmarks under different thermodynamic paths.
• To determine the relationship between these landmarks and the growth of dynamical heterogeneity.

Main Methods:

• Molecular dynamics simulations of glass-forming liquids.
• Analysis of dynamical slowdown under varying temperature (cooling) and pressure (compression).
• Identification and comparison of dynamical landmarks: Arrhenius-to-non-Arrhenius crossover and inflection point.

Main Results:

• Evidence of distinct microscopic routes for dynamical slowdown under cooling and compression.
• A previously unrecognized discrepancy between the Arrhenius-to-non-Arrhenius crossover (cooling) and the inflection point (compression).
• Simulations show the inflection point is more directly correlated with the growth of dynamical heterogeneity than the crossover.

Conclusions:

• Dynamical slowdown in glass-forming liquids is path-dependent, with cooling and compression revealing different behaviors.
• The dynamic facilitation framework is supported even at small supercoolings.
• The inflection point under compression is a more direct indicator of dynamical heterogeneity growth.