What are Microclusters ?

Abstract

Classification of the fragments which are obtained by successive division of material is given according to their sizes. The particles are called fine particles when they consist of the order of 10³ ÷ 10⁵ atoms¹. They exhibit properties different from those of the material before division at low temperatures. The problem has to be treated statistically, as we are unable to pick up fine particles of a given shape: they have uncontrollable surface irregularity. On the other hand, particles called microclusters when they consist of 10 ÷ 10³ atoms show quantum-mechanical properties that depend upon their shape like atoms and molecules. Microclusters of given shape and size can, in principle, be extracted, and their properties can be measured. Microclusters exhibit, at finite temperatures, physical properties often encountered in macroscopic systems like liquids. This is due to the presence of a large number of low-lying metastable states. Finally, recent observations of the shell periodicity of an atomic structure in grown microclusters are presented.