Comparison of the optical response of hydrogen-passivated germanium and silicon clusters

We present the calculation of the optical response of hydrogen-passivated germanium and silicon clusters using time-dependent density functional theory in the adiabatic local density approximation. The optical response, optical gaps, and other quantities of interest of Ge clusters are compared with the corresponding results for the Si clusters. Our most notable find is that in the low-energy region there are significant differences. More specifically, the Ge clusters exhibit higher oscillator strength and their energy gaps are smaller compared to Si clusters. The overall shape of the optical response of Ge clusters is very similar to that of Si clusters. We conclude that many similarities and differences of these clusters originate from the optical response of the corresponding bulk materials.