Preferred structures in small particles

Morphological transformations of Au particles supported on SiO were observed by real-time high-resolution electron microscopy, and the data were analysed quantitatively to extract the relative probabilities of the different morphologies and compared with a probability model to understand the role of the different parameters that affect the transformations. The experimental data and probability model show good agreement and reveal several interesting trends for the first time. The single crystal population dominates over the icosahedral multiply twinned particles (Ic) and the decahedral multiply twinned particles (Dc) over the observed size regime 2-8 nm. The Ic shows a maximum in relative probability of occurrence at smaller sizes, whereas the Dc probability increases with size, leading to a transition region centred at 6·5 nm particle diameter at which Dc and Ic show almost equal relative probabilities. The activation energies of the morphologies are also affected by the surface stress and anisotropy of the surface free energies.