Real-Time KMC Simulation of Vacancy-Mediated Intermixing in Au@Ag Octahedral Core-Cubic Shell Nanocrystals with Ab...

Area of Science:

• Materials Science
• Nanotechnology
• Computational Chemistry

Background:

• Core-shell nanocrystals (NCs) offer tunable properties but are susceptible to compositional changes via intermixing.
• Intermixing can degrade the performance of NCs in various applications.
• Previous modeling approaches had limitations in accuracy and scope.

Purpose of the Study:

• To develop a predictive, atomistic-level model for vacancy-mediated intermixing in core-shell NCs.
• To incorporate ab initio density functional theory calculations for thermodynamics and diffusion barriers.
• To understand the time scale and rate-controlling processes of intermixing.

Main Methods:

• Developed a stochastic model for vacancy-mediated intermixing.
• Integrated ab initio density functional theory (DFT) for vacancy formation and diffusion barriers.
• Simulated intermixing on relevant time scales (10^1-10^3 s).
• Applied the model to gold-silver (Au@Ag) core-shell nanocrystals.

Main Results:

• The model accurately predicts the experimentally observed intermixing time scale of ~100 s at 450 °C for 60 nm Au@Ag NCs.
• Elucidated the specific rate-controlling processes governing intermixing.
• Determined the effective intermixing barrier based on atomistic interactions.

Conclusions:

• The developed model provides a comprehensive understanding of intermixing in core-shell NCs.
• This approach overcomes limitations of previous generic or continuum models.
• Enables predictive insights into nanocrystal stability and property evolution for tailored applications.