Universal divergenceless scaling between structural relaxation and caged dynamics in glass-forming systems

Area of Science:

• Condensed Matter Physics
• Materials Science
• Computational Chemistry

Background:

• Glass transition involves a dramatic increase in structural relaxation time (tau(alpha)).
• Microscopic dynamics near the glass transition are characterized by rattling within a cage of neighbors.

Purpose of the Study:

• Investigate the correlation between structural relaxation time (tau(alpha)) and rattling amplitude (Debye-Waller factor).
• Develop an analytical model for the master curve of structural relaxation.
• Explore the role of equilibrium and supercooled states in glass transition dynamics.

Main Methods:

• Molecular-dynamics simulations of a model polymer and a binary mixture.
• Systematic variation of temperature, density, potential, and polymer length.
• Analysis of structural relaxation, rotational, and translational diffusion.

Main Results:

• Evidence of scaling between structural relaxation and caged dynamics across various glassformers.
• Development of an analytical model for the master curve using characteristic length scales.
• Experimental validation of simulation results over 18 orders of magnitude in relaxation times.
• Rejection of density scaling proportionality (rho(-1/3)) for characteristic length scales.

Conclusions:

• Equilibrium and supercooled states hold crucial information about relaxation slowdown near the glass transition.
• Simulated dynamics near glass transition align with Lindemann melting criterion and free-volume models.
• The developed model does not predict divergences in structural relaxation time.