Molecular polarizability of semiconductor clusters and nanostructures

The interacting-induced-dipoles polarization model implemented in program PAPID is used for the calculation of the molecular dipole–dipole polarizability View the MathML source. The method is tested with View the MathML source and GanAsm small clusters. On varying the number of atoms, the clusters show numbers indicative of particularly polarizable structures. The results for the polarizability are in agreement with reference calculations from Chelikowsky. The bulk limit for the polarizability is estimated from the Clausius–Mossotti relationship. The polarizability trend for these clusters as a function of size is different from what one might have expected. The clusters are all more polarizable than what one might have inferred from the bulk polarizability. Previous experimental work has yielded the opposite trend for somewhat larger clusters, i.e., in this work the polarizability of clusters tends to be lower than the bulk limit and approaches this limit from below. At present, the origin of this difference is problematic. One might argue that smaller clusters need not behave like those of intermediate size. The high polarizability of small clusters is attributed to dangling bonds at the surface of the cluster. Indeed, most of the atoms within small clusters reside on the surface. In this respect, semiconductor clusters resemble metallic clusters.