  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.
