Dynamics and Kinetics of Nanoparticle Growth
Overview
Shape control is important in utilizing the structure-property relationship of nanocrystals. High surface-to-volume ratio of nanocrystals induces dynamic surface reactions on exposed facets of nanocrystals, such as adsorption, desorption and diffusion of surface atoms, all of which are important in overall shape transformation. However, it is difficult to track shape transformation of nanocrystals and understand the underlying mechanism at the level distinguishing events on individual facets. We investigate changes of individual surface-exposed facets during diverse shape transformations of Au nanocrystals using kinetic Monte Carlo simulations. Our goal is to understand how the chemical potential, bond energy, and surface diffusion affect the overal shape of nanocrystals.
Figure 1. Growth progression of a nanocrystal with circular (top row), square (middle row), and equilateral triangle (bottom row) cross-section in 111 plane, which leads to the final configuration of a hexagon. Snapshots in A-E were taken from kinetic Monte Carlo simulations at nondimensionalized time t=0, 100, 200, 300, and 400 time points, respectively.
Movie 1. Formation of stable facets, and disapearance of unstable facets are captured in this kinetic Monte Carlo simulation with 111 direction being perpendicular to the screen, where a triangular seed nanocrystal is growing and tranforming to a hexagonal nanocrytal.