Comparative study of microstructural evolution during melting and crystallization.

Area of Science:

• Materials Science
• Computational Physics
• Nanotechnology

Background:

• Nanocrystalline materials exhibit unique properties due to their high surface area and grain boundary density.
• Understanding phase transitions in these materials at the atomic scale is crucial for controlling their behavior.

Purpose of the Study:

• To investigate the atomic-scale mechanisms of isothermal melting in nanocrystalline silver.
• To analyze the process of crystallization from a supercooled liquid state.
• To elucidate the structural evolution during these phase transitions.

Main Methods:

• Atomistic simulations using molecular dynamics (MD).
• Employing a modified analytic embedded atom method (MEAM) for interatomic interactions.
• Utilizing radial distribution function (RDF) and common neighbor analysis (CNA) for structural characterization.

Main Results:

• Melting in nanocrystalline silver initiates at grain boundaries and proceeds continuously.
• Characteristic bond pairs indicative of liquid or liquid-like phases increase linearly during melting.
• Crystallization from supercooled liquid exhibits three distinct stages: nucleation, rapid growth, and slow relaxation.
• Homogeneous nucleation is observed at higher supercooling, influencing crystallization and texture.

Conclusions:

• Grain boundary networks are key to initiating melting in nanocrystalline silver.
• The crystallization process from a supercooled liquid is well-defined and can be modeled by the Johnson-Mehl-Avrami equation.
• Atomic-scale simulations provide critical insights into phase transitions in nanomaterials.