Atomic-Scale Structure and Stress Release Mechanism in Core-Shell Nanoparticles.

Area of Science:

• Materials Science
• Nanotechnology
• Computational Chemistry

Background:

• Core-shell nanoparticles are crucial for catalysis, sensors, and theranostics.
• Current imaging techniques cannot fully resolve their internal 3D atomic structure.

Purpose of the Study:

• To analyze atomic positions and stress-release mechanisms in cubic Au-Pd core-shell nanoparticles.
• To achieve resolution approximately 1000 times higher than existing experimental methods.

Main Methods:

• Large-scale molecular dynamics simulation of a 73 nm cubic Au-Pd core-shell nanoparticle.
• Modeling epitaxial deposition of a 4 nm Pd shell onto a 65 nm Au core.
• Utilizing reliable interatomic potentials for accurate simulation.

Main Results:

• Identified specific deformations and stress relaxation due to lattice mismatch (+4.8%) and interface confinement.
• Observed long-range bending of atomic rows, Pd shell bulging, and stacking faults at corners.
• Strain is significantly higher on facets compared to edges and corners, impacting properties.

Conclusions:

• The detailed 3D atomic structure and stress release mechanisms are elucidated.
• Findings are consistent with experimental data and provide a basis for future experimental verification.
• The simulation methods are applicable to other core-shell nanoparticles with fcc structures and varying shapes.