Changing shapes in the nanoworld
What are the mechanisms leading to the shape relaxation of three-dimensional crystallites? Kinetic Monte Carlo simulations of fcc clusters show that the usual theories of equilibration, via atomic surface diffusion driven by curvature, are verified only at high temperatures. Below the roughening temperature, the relaxation is much slower, kinetics being governed by the nucleation of a critical germ on a facet. We show that the energy barrier for this step linearly increases with the size of the crystallite, leading to an exponential dependence of the relaxation time.
Combe
N
Departement de Physique des Materiaux, UMR CNRS 5586, Universite Claude Bernard Lyon-1, 69622 Villeurbanne Cedex, France.
Jensen
P
Pimpinelli
A