Single-particle fluctuations and directional correlations in driven hard-sphere glasses.

Area of Science:

• Soft Matter Physics
• Materials Science
• Computational Physics

Background:

• Understanding the dynamics of glassy materials is crucial for materials science.
• Hard-sphere glasses provide a fundamental model system for studying glass transitions and shear-induced phenomena.

Purpose of the Study:

• To investigate the dependence of single-particle fluctuations and dynamic correlations on packing fraction and shear rate in hard-sphere glasses.
• To explore the interplay between shear and thermal fluctuations in governing glass dynamics.
• To analyze the anisotropy of dynamic correlations under shear.

Main Methods:

• Event-driven molecular dynamics simulations.
• Experimental studies on hard-sphere systems.
• Analysis of single-particle jump distributions and dynamic four-point correlations.

Main Results:

• Above the glass transition, decreasing shear rate enhances dynamic correlations, broadening the exponential tail of single-particle jumps.
• Decreasing packing fraction also broadens the exponential tail but reduces dynamic heterogeneity.
• A competition between shear and thermal fluctuations explains the observed behaviors.

Conclusions:

• The dynamics of hard-sphere glasses under shear are complex and depend on both packing fraction and shear rate.
• Shear and thermal fluctuations play competing roles in determining particle dynamics.
• Dynamic correlations exhibit anisotropic behavior under shear.