Theoretical models of silica nanorings: First-principles calculations

We performed first-principles calculations on silica nanorings (NRs) designed via the assembly of two- (2MR), three- (3MR), four- (4MR), and six-membered rings (6MR) in a number of different ways. The stable configurations, energetics, and electronic structures of these NRs are presented. The most stable configurations were found to be size-dependent and to possess different structural features at different size ranges. For small-size silica NRs (SiO₂)_n with n <12, the configurations with 2MR-3MR hybrid structures (2-3MR-NRs) were energetically most stable. For 12 <n <22, the NRs formed from linked 2MRs (2MR-NRs) became most favorable. For n > 22, the configurations composed of uniformly hybrid 2MRs and 4MRs (2-4MR-NRs) were the most stable structures. The 2-4MR-NRs had the narrowest HOMO-LUMO gaps, which decreased with decreasing n. © 2008 American Chemical Society.