Atomic Structure of Small Clusters : The Why and How of the Five-Fold Symmetry
Particles with pentagonal symmetry which have been observed by microscopy in metal deposits possess the normal fcc structure, as revealed by electron diffraction. However, at the first stage of their formation, a nucleus with anomalous structure was existing, this structure being related with the nucleus shape. The structure characteristic of the ico-sahedral shape has been effectively observed by electron diffraction in Ar clusters comprising a few hundreds of atoms. For a given number of atoms this structure proves to be more stable than that of small fcc microcrys-tals since at the expense of some elastic distortions and twin formation, it allows a better surface energy. However, this structure cannot be grown up to macroscopic sizes due to the compression of the central region by external layers.
KeywordsAdditional Atom Pentagonal Bipyramid Elastic Distortion Icosahedral Cluster Macroscopic Size
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