Determination of the ground-state atomic structures of size-selected au nanoclusters by electron-beam-induced transformation.

The equilibrium ground state atomic structures of nanoparticles are critical to understanding the relationship between their structure and functionality, e.g., in catalysis, and are the standard output of first principles and semiempirical theoretical treatments. We demonstrate a method of obtaining a stable population of the structural isomers of supported Au clusters from a metastable initial array via electron beam irradiation. Statistical investigation of size-selected Au clusters containing 923±23 atoms via aberration-corrected scanning transmission electron microscopy shows that virtually all of the icosahedral (Ih) clusters undergo structural transformations into decahedral (Dh) (primarily) or fcc isomers while Dh and FCC clusters generally retain their atomic structures after electron irradiation of each cluster individually for up to 400 s at a dose of 2.4×10(4)  e-/angstrom2/frame. Intermediate phases are often observed in the image series (videos) before the appearance of the new stable isomers, the relative structural populations of which can be controlled via the electron beam dose. The comprehensive results reported here should provide a valuable experimental reference for testing or refining potential models and for kinetic or dynamical treatments of the atomic configurations.