Theoretical study of silicon-oxygen-sulfur ionic oligomers (SiOS)n+ and (SiOS)n- (n = 1-6)

The geometrical structures and relative stability of the various possible isomers of silicon-oxygen-sulfur ionic oligomers, (SiOS)n+ and (SiOS)n- (n = 1-6), were studied using quantum chemistry calculations. The ground state of the monomer is a triangular molecule, and that of the dimmer is a rhombic 4MR with two S atoms ending the same Si atom. The most stable isomers for the trimer and tetramer anionic clusters are simply extensions of the rhombic structure, while the tetramer cationic cluster becomes the linear 4MRs with one Si-S defect at the each side. However, for n = 5 and n = 6, the hybrid structures by the 4MRs and hexagonal six-membered ring (6MR) become energetically most favorable configurations. These distinctive structural geometries would provide guide for future experimental detections of these small Si-O-S ionic oligomers.