Controlled synthesis of metallic nanocrystals allows tuning of shapes and thus properties for applications, e.g., to catalysis and plasmonics. However, these shapes are metastable. Far-from-equilibrium evolution back to equilibrium Wulff shapes is mediated by surface diffusion, and is highly sensitive to the numerous atomistic-level diffusion barriers for diverse local surface configurations. Thus, realistic description of surface diffusion kinetics is thus crucial to predict the stability of non-equilibrium nanocrystal shapes, a prerequisite for functionality in applications. A stochastic lattice-gas model was developed incorporating realistic values for the multiple barriers for terrace, edge, and interlayer diffusion (contrasting previous generic bond counting prescriptions) based upon insights from homoepitaxial film growth. [Phys. Rev. Materials <b>3 </b>(2019), 026001] In this talk, we will describe the model, and apply kinetic Monte Carlo (KMC) simulations to assess: reshaping of Ag nanocubes to Wulff polyhedra mediated by nucleation of new {100} facets; the pinch-off of sufficiently elongated Ag nanorods; and key aspects of sintering for orientationally-aligned Ag or Au nanoclusters. The time scale for sintering of ~4 nm Au nanoclusters observed in HR-TEM studies was also recovered.

Reshaping and sintering of 3D fcc metal nanocrystals: Stochastic atomistic modeling with realistic surface diffusion kinetics

2019 Fall National Meeting

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