Structure of 1 nm silver clusters

Small silver clusters have been investigated by electron microscopy. A bimodal size distribution is formed containing particles of diameter 1-2 nm and 4-8 nm. Among the largest particles icosahedra and cuboctahedra appear with equal frequency in HREM. 1 nm size icosahedra, however, could not be found, while cuboctahedra of this size could be resolved. Computer simulations of high resolution images for both structures reveal that icosahedra are more difficult to resolve under the experimental conditions. A dilation of approximately 5% of the lattice parameter could be measured for 1 nm particles. For 2 nm particles, this dilation drops to 2.5% compared with the bulk value of the particles larger than 3 nm.