Calculated polarizabilities of intermediate-size Si clusters

We have used a first-principles, density-functional-based method to calculate the electric polarizabilities and dipole moments for several low-energy geometries of Si clusters in the size range $10<~N<~20$. The polarizability per atom is found to be a slowly varying, nonmonotonic function of N. Over this size range the polarizability appears to be correlated most strongly to cluster shape and not with either the dipole moment or the highest occupied–lowest unoccupied molecular-orbital gap. The calculations indicate that the polarizability per atom for Si clusters approaches the bulk limit from above as a function of size.