Tetrahedrality Dictates Dynamics in Hard Sphere Mixtures.

Area of Science:

• Physics
• Materials Science
• Physical Chemistry

Background:

• The relationship between local structure and dynamical slowdown in glassy fluids remains a long-standing challenge.
• Predicting fluid dynamics solely from local structural features is currently lacking a simple, effective method.

Purpose of the Study:

• To develop a simple method for predicting the dynamical behavior of hard sphere mixtures based on local structural properties.
• To establish a direct link between local structural features and the global diffusivity of glassy fluids.

Main Methods:

• Utilized packing fraction and a novel order parameter quantifying local tetrahedrality.
• Analyzed hard sphere mixtures, a fundamental class of glass formers.

Main Results:

• Accurately predicted fluid diffusivity using packing fraction and the tetrahedrality order parameter.
• Demonstrated a direct correlation between the number of tetrahedral clusters and global diffusivity.
• Showed that the tetrahedrality parameter can identify regions of high and low particle mobility within the system.

Conclusions:

• Local tetrahedrality is a powerful predictor of both local and global dynamics in hard sphere mixtures.
• The stability of tetrahedral clusters, fundamental building blocks in disordered fluids, underlies their predictive power for dynamics.