  The electronic structure and absorption spectrum of hydrogenated silicon
carbide nanocrystals (SiCNC) have been determined by first principles
calculations. We show that the reconstructed surface can significantly change
not just the onset of absorption, but the \emph{shape} of the spectrum at
higher energies. We found that the absorption treshold of the reconstructed
SiCNs cannot be accurately predicted from traditional density functional theory
calculations.
