Effects of local fields in time-dependent density functional theory shown in oxidized silicon clusters

We studied the influence of oxygen and oxygen-related bonds on the structural, electronic, and optical properties of a prototypical silicon dot, the adamantanelike Si10H16 nanocrystal. The optical photoabsorption spectra have been calculated keeping into account both local field effects and the effects of pseudopotential nonlocality. While the effects of the latter show up essentially as a change of a few percent of the f-sum rule integral, the former are shown to modify substantially both the optical absorption edge and the size of its redshift as induced by oxidation of the nanocrystal. Exchange-correlation contributions have also been evaluated, within the adiabatic local density approximation.