Two- and three-membered-ring hybrid structures of silica nanoclusters

Silica nanoclusters based on uniformly hybrid two- (2MR) and three-membered-ring (3MR) units have been studied. These nanoclusters may present with well-defined stoichiometric ringed, porous (tubular), and cagelike structures. Our density functional calculations demonstrate that the 2MR and 3MR hybrid clusters are energetically more favorable than the pure 2MR or 3MR clusters revealed early. These 2MR and 3MR hybrid clusters, in particular, the cagelike, would be considered as energetically favorable structural models of silica nanoclusters. They possess distinctive IR spectra, characterized by a sharp peak at the vicinity of 1050 cm^-1 for the clusters with nonbridging oxygen (NBO) defects and by two strongest peaks at the 950-980 cm^-1 and 1030-1050 cm^-1 regions, respectively, for the fully coordinated structures.