Ab initio calculations for the absorption spectra and polarizabilities of small sulfur clusters

Absorption spectra for Sn clusters （n=2...8） are calculated using an adiabatic time-dependent density functional formalism within the local density approximation （LDA）. We compare the calculated spectra with those computed using a simple LDA approach. The time-dependent LDA （TDLDA） spectra display a significant blue shift with respect to the LDA spectra. The calculated spectra present a variety of features that can be used for comparison with future experimental investigations. We also obtain a significant threshold absorption, which can distinguish between different ground states of the sulfur clusters. In addition, the polarizabilities of the clusters are calculated by using the higherorder finite-difference pseudopotential density functional method in real space. We find that the polarizabilities of the clusters considered are higher than the value estimated from the ＇hard sphere＇ model using the bulk static dielectric constant. The computed polarizabilities per atom tend to decrease with increasing cluster size. The polarizabilities are closely related to the HOMO-LUMO gaps and the geometrical configurations.

Ab initio calculations for the absorption spectra and polarizabilities of small sulfur clusters

Absorption spectra for S₂ clusters (n=2ldots8) are calculatedusing an adiabatic time-dependent density functional formalism withinthe local density approximation (LDA). We compare the calculatedspectra with those computed using a simple LDA approach. Thetime-dependent LDA (TDLDA) spectra display a significant blue shiftwith respect to the LDA spectra. The calculated spectra present avariety of features that can be used for comparison with futureexperimental investigations. We also obtain a significant thresholdabsorption, which can distinguish between different ground states ofthe sulfur clusters. In addition, the polarizabilities of theclusters are calculated by using the higher-order finite-differencepseudopotential density functional method in real space. We find thatthe polarizabilities of the clusters considered are higher than thevalue estimated from the `hard sphere' model using the bulk staticdielectric constant. The computed polarizabilities per atom tend todecrease with increasing cluster size. The polarizabilities areclosely related to the HOMO--LUMO gaps and the geometricalconfigurations.