Impurity diffusion in magic-size icosahedral clusters.

Area of Science:

• Materials Science
• Computational Chemistry
• Nanotechnology

Background:

• Atomic diffusion governs chemical ordering in nanoalloys, impacting their thermodynamic properties and evolution from non-equilibrium states.
• Understanding atomic-level diffusion mechanisms is essential for controlling nanoalloy behavior and experimental outcomes.

Purpose of the Study:

• To investigate atomic diffusion pathways of single-atom impurities (Ag or Au) within magic-size icosahedral clusters (Cu or Co).
• To elucidate the mechanisms driving diffusion and their relationship to the cluster's structural and thermodynamic properties.

Main Methods:

• Employed molecular dynamics and metadynamics computational techniques.
• Simulated the movement of single-atom impurities within pure icosahedral metal clusters.

Main Results:

• Discovered unexpected diffusion pathways where impurity displacement is coupled with vacancy creation in the cluster's core.
• Identified a novel diffusion mechanism distinct from previously known vacancy-mediated processes.
• Correlated the observed diffusion with non-homogeneous compressive stress within the icosahedral structure.

Conclusions:

• The study reveals a new atomic diffusion mechanism in nanoalloys, challenging existing models.
• Internal stress within icosahedral clusters plays a significant role in mediating impurity diffusion.
• Findings provide critical insights into the thermodynamic behavior and evolution of nanoalloys.