Dynamics of probes in model glassy matrices

Area of Science:

• Condensed matter physics
• Computational materials science

Background:

• Understanding molecular dynamics in amorphous materials is crucial for materials science.
• Previous models often simplify matrix interactions, limiting applicability to complex systems.

Purpose of the Study:

• To investigate the diffusion dynamics of diatomic probe molecules in a model hard-sphere matrix.
• To explore the transition in diffusion behavior as matrix connectivity changes.

Main Methods:

• Molecular dynamics simulations were employed to model the system.
• The connectivity of matrix particles was systematically varied using string lengths (l).
• Probe diffusion coefficients (D) and single-particle dynamics were analyzed.

Main Results:

• Diffusion coefficient (D) smoothly interpolates between fluid and glass limits.
• A transition from power-law to Arrhenius dependence of D was observed as l decreased.
• Hopping motion becomes dominant at a critical length (l(c)), leading to Arrhenius behavior.
• Dynamic heterogeneity was present despite the absence of a growing dynamic correlation length.

Conclusions:

• Matrix connectivity significantly influences probe molecule diffusion.
• The study provides insights into the mechanisms of molecular transport in disordered materials.
• Observed dynamic heterogeneity highlights complex dynamics in systems lacking long-range order.