Spectroscopic Properties of Chalcopyrite Nanoparticles

An approach is presented to construct stoichiometric and saturated clusters as representative models for nanoparticles based on quantum-chemical surface energy calculations. The procedure consists of three steps. In the first step, the shape of the cluster is determined by applying the Wulff theorem based on calculated surface energies of the solid compound. Stoichiometry is recovered by adding selected atoms on the cluster surface. If the particles in solution are to be modeled, solvent molecules may be added. A global optimization is then performed to allow for full reconstruction of the cluster structure. As an example, we studied the spectroscopic properties of chalcopyrite (CuFeS2) nanoparticles and compared our calculated results to experimental O 1s X-ray photoelectron spectroscopy, IR, and optical spectra.