πBonding and Delocalization Effects in SiO2Polymorphs

Abstract

The bond polarizability in Si${\mathrm{O}}_2$ polymorphs increases as the Si-O-Si bond angle increases and as the density decreases. This increase and systematic variations in other properties are due to $\pi$ bonding between Si and O. Delocalization of $\pi$ electrons in Si-O ring configurations and bond strain determine the properties of polymorphs of density under 2.33 g ${\mathrm{cm}}^{-3\mathrm{}}$; they are also responsible for the pressure and irradiation behavior of Si${\mathrm{O}}_2$.