A transferable nonorthogonal tight-binding model of germanium:   application to small clusters
  We have developed a transferable nonorthogonal tight-binding total energy model for germanium and use it to study small clusters. The cohesive energy, bulk modulus, elastic constants of bulk germanium can be described by this model to considerably good extent. The calculated bulk phase diagram for germanium agrees well with LDA results. The geometries and binding energies found for small Ge$_n$ clusters with $n=3-10$ are very close to previous {\em ab initio} calculations and experiments. All these results suggest that this model can be further applied to the simulation of germanium cluster of larger size or with longer time scale, for which {\em ab initio} methods is much more computational expensive. 
Jijun Zhao, Jinlan Wang, Guanghou Wang