Alpha-relaxation by scattering and medium-range atomic correlation in simple liquids

Area of Science:

• Condensed matter physics
• Materials science
• Computational physics

Background:

• Relaxation dynamics in liquids and glasses are crucial for understanding material properties.
• Inelastic X-ray/neutron scattering probes these dynamics via the intermediate scattering function F(Q, t).
• The alpha-relaxation time (τα) is typically measured at the first peak of S(Q) and linked to bulk viscosity and atomic caging.

Purpose of the Study:

• To investigate the factors influencing the alpha-relaxation time (τα) determined by scattering experiments.
• To differentiate the contributions of viscosity, spatial cooperativity, and atomic caging to τα.
• To explore the role of medium-range order in atomic caging dynamics.

Main Methods:

• Molecular dynamics simulations of metallic liquids.
• Analysis of the intermediate scattering function F(Q, t).
• Characterization of atomic caging and spatial cooperativity.

Main Results:

• The alpha-relaxation time (τα) derived from scattering experiments is not solely indicative of viscosity.
• Spatial cooperativity significantly influences the measured τα.
• Atomic caging involves cooperative dynamics of medium-range order, extending beyond nearest neighbors.

Conclusions:

• Scattering-derived τα provides insights into both viscosity and cooperative dynamics.
• The concept of atomic caging needs to incorporate medium-range order effects.
• Understanding these complex dynamics is essential for predicting liquid and glass behavior.