Abstract
A kinetic Monte Carlo approach on a coarse-grained lattice is developed for the simulation of surface diffusion processes of Ni, Pd and Au structures with diameters in the range of a few nanometers. Intensity information obtained via standard two-dimensional transmission electron microscopy imaging techniques is used to create three-dimensional structure models as input for a cellular automaton. A series of update rules based on reaction kinetics is defined to allow for a stepwise evolution in time with the aim to simulate surface diffusion phenomena such as Rayleigh breakup and surface wetting. The material flow, in our case represented by the hopping of discrete portions of metal on a given grid, is driven by the attempt to minimize the surface energy, which can be achieved by maximizing the number of filled neighbor cells.Graphical abstract
Highlights
Metallic particles in the range of a few nanometers straddle the line between microscopic and quasi-classical systems
A kinetic Monte Carlo approach on a coarse-grained lattice is developed for the simulation of surface diffusion processes of Ni, Pd and Au structures with diameters in the range of a few nanometers
Regarding the shape and structure of metallic nanoparticles, modern imaging techniques of electron microscopy yielded significant advances in the experimental study of these transitions with particle size [2], and opened the possibility for the in-situ analysis of structural changes caused by chemical interactions or temperaturemediated diffusion processes [3]
Summary
Metallic particles in the range of a few nanometers straddle the line between microscopic and quasi-classical systems. Instead of describing the motion of each atom separately, which introduces clear limitations to the number of particles involved in standard molecular dynamics simulations, we employ a coarse-grained model which handles material transfer in larger groups of atoms, defined by the grid size of the CA This reduces, together with the intrinsic limitation to interactions with next-neighbor cells, the computational effort significantly, and allows the simulation of temperature-induced effects such as droplet formation, surface tension and Rayleigh-breakup for even. An attempt is made to reconstruct the actual shapes from two-dimensional TEM images and compare them to the model predictions
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