Observation of Bridging Chlorine in Vitreous SiO2

The short-range to mid-range structure of inorganic glasses profoundly impacts their physical properties. In this work, we have used multiple spectroscopic methods to examine the change in the network structure of amorphous silica with addition of Cl. Unlike analogous F-doped silicas, where the bonding of halogen leads to terminal Si–F groups, NMR and Raman data for Cl-doped v-SiO₂ indicate bridging between silica tetrahedra, preserving rather than reducing network connectivity and contributing to their elastic stiffness and viscosity behaviors. These bridging Cl atoms make v-SiO₂ stiffer while having the same effect on density behavior per mol % dopant as F in v-SiO₂ and thus may be a desirable attribute in tailoring v-SiO₂ for optical applications.