Metal-Encapsulated Caged Clusters of Germanium with Large Gaps and Different Growth Behavior than Silicon

Metal ([Formula presented])-encapsulated caged clusters of Ge are studied using the ab initio pseudopotential plane-wave method and the generalized gradient approximation for the exchange-correlation energy. Depending upon the size of the [Formula presented] atom, we find Frank-Kasper polyhedral [Formula presented] for [Formula presented], Zr, Hf, and capped decahedral or cubic [Formula presented] and [Formula presented] clusters for several [Formula presented] atoms. The growth behavior differs from the one found in [Formula presented] clusters. The highest-occupied–lowest-unoccupied molecular orbital gaps are, however, similarly large or even higher in some cases. [Formula presented] and [Formula presented] are magnetic. The weak interaction between the clusters makes such species attractive for cluster assembled materials.