Optical Properties of Organosilicon Compounds Containing Sigma-Electron Delocalization by Quasiparticle Self-Consistent GW Calculations

We investigate theoretically the electronic and optical absorption properties of two sub-classes of oligosilanes: (i) Si(CH3)4, Si4(CH3)8, and Si8(CH3)8 that contain Si dot, ring and cage, respectively, and exhibit typical SiC and SiSi bonds; and (ii) persilastaffanes Si7H6(CH3)6 and Si12H6(CH3)12, which contain extended delocalized σ-electrons in SiSi bonds over three-dimensional Si frameworks. Our modeling is performed within the GW approach up to the partially self-consistent GW0 approximation, which is more adequate for reliably predicting the optical band gaps of materials. We examine how the optical properties of these organosilicon compounds depend on their size, geometric features, and Si/C composition. Our results indicate that the present methodology offers a viable way of describing the optical excitations of tailored functional Si-C-based clusters and molecular optical tags with potential use as efficient light absorbers/emitters in molecular optical devices.