Influence of 5-atom rings on the optical properties of amorphous carbon nitride

The optical properties of three amorphous tetrahedral carbon-based clusters of the type a-C17-iNiH24 with 5-atom rings have been calculated. The hydro gens are used to passivate the outermost dangling bonds and i is 0, 1 or 4. The theoretical DFT-LDA based method used minimizes the energy of the clus ters and provides the energy spectrum and the optical transitions for the m inimum energy structures. The optical absorption spectrum of each cluster i s analyzed and a comparison is made with previously reported spectra for cl usters with 6-atom boat-type rings in order to see the influence of the pre sent atomic topology.