Small particles in gaseous systems are called clusters, aerosols, dust particles, Aitken particles, etc., depending on their size, the media where they are observed, and the field of science in which they are studied. Below we call clusters systems of bound atoms or molecules containing from several atoms (molecules) up to thousands, so that their structure can be essential for determining their properties. If clusters are like bulk systems, we call them small particles. The principal pecu liarity of clusters is with respect to magic numbers of cluster atoms that correspond to a heightened...