Intermittent cluster dynamics and temporal fractional diffusion in a bulk metallic glass

Area of Science:

• Materials Science
• Condensed Matter Physics
• Physical Chemistry

Background:

• Glassy solids undergo physical aging, transitioning to lower-energy states.
• Characterizing structural relaxation times is crucial for understanding time-dependent properties.

Purpose of the Study:

• To investigate atomic-scale micro-structural rearrangements during physical aging in metallic glasses.
• To identify the transport mechanisms governing relaxation processes at extended timescales.

Main Methods:

• Coherent X-ray scattering experiments over 300,000 seconds to track atomic rearrangements.
• Atomistic simulations to complement experimental observations.

Main Results:

• Demonstrated emergence of sub-diffusive anomalous transport and temporal fractional diffusion.
• Observed a transition from stretched exponential to power-law behavior at long decorrelation times.
• Revealed collective and intermittent atomic motion.

Conclusions:

• Provided a physical basis for classical stretched exponential relaxation.
• Uncovered a new power-law governed collective transport regime in metallic glasses.
• Challenged conventional frameworks of homogeneous aging and atomic diffusion.