Abstract：

Clusters contain more than just some few atoms but not so many that they can be considered infinite. By varying their size, their properties can often be varied in a more or less controllable way. Often, however, the precise relation between size and property is largely unknown: the sizes of the systems are below the thermodynamic limit. Theoretical studies of such systems can provide relevant information, although in many cases idealized systems have to be treated. The challenge of such calculations is the combination of the relatively large size of the systems together with an often unknown structure.

In this presentation, different theoretical methods for circumventing these problems shall be discussed. They shall be illustrated through applications on various types of clusters. These include isolated metal clusters with one or two types of atoms, metal clusters deposited on a surface, nanostructured HAlO, and semiconductor nanoparticles.