Structures, Stabilities and Electronic Properties of Nanobuilding Blocks Vinyl Silsesquioxanes: A Density Functional Theory Study

Abstract

First-principle calculations on nanobuilding blocks vinyl silsesquioxanes Si 2n O 3n (CHCH 2 ) 2n (n = 1-5) have been performed using density functional theory (DFT), in order to study their structures, electronic and vibrational properties. The energy differences between the possible conformers of the same size vinyl silsesquioxanes are small. The large HOMO-LUMO gaps, which range from 5.00 to 6.93 eV, imply optimal electronic structures for these molecules. The highest occupied molecular orbitals (HOMOs) are mostly contributed by the vinyl orbitals for all the vinyl silsesquioxanes Si 2n O 3n (CHCH 2 ) 2n except for Si 2 O 3 (CHCH 2 2 , for which it is composed of oxygen p-type atomic orbitals. The lowest unoccupied molecular orbitals (LUMOs) are mainly occupied and dominated by the vinyl * orbitals for all the vinyl silsesquioxanes Si 2n O 3n (CHCH 2 ) 2n (n = 1-5). The infrared spectra of the vinyl silsesquioxanes are also discussed.