Morphology transition mechanism from icosahedral to decahedral phase during growth of nanoclusters
The study of metal nanoclusters has been a subject of intense research activities in recent years. This is due to their great importance in variety of applications. Besides, such objects are intermediate between single atoms and molecules and bulk matter, and their properties may qualitatively differ. Properties of nanocluster crucially depend on growth methods and conditions during the process. Understanding of the growth process at the early stages is of particular interest since the morphology of the seed may determine structure of big clusters.
The morphology transition from the thermodynamically favorable to the unfavorable phase during growth of free-standing copper nanoclusters is studied by molecular dynamics simulations. We give a detailed description of the kinetics and thermodynamics of the process. A universal mechanism of a solid-solid transition, from icosahedral to decahedral morphology in nanoclusters, is proposed. We show that a formation of distorted NC during the growth process with islands of incoming atoms localized in certain parts of the grown particle may shift the energy balance between Ih and Dh phases in favour of the latter leading to the morphology transition deep within the thermodynamic stability field of the former. The role of diffusion in the morphology transition is revealed. In particular, it is shown that fast diffusion should suppress the morphology transition and favour homogeneous growth of the nanoclusters.