Electronic, Structural, and Mechanical Properties of SiO2 Glass at High Pressure Inferred from its Refractive Index

We report the first direct measurements of the refractive index of silica glass up to 145 GPa that allowed quantifying its density, bulk modulus, Lorenz-Lorentz polarizability, and band gap. These properties show two major anomalies at similar to 10 and similar to 40 GPa. The anomaly at similar to 10 GPa signals the onset of the increase in Si coordination, and the anomaly at similar to 40 GPa corresponds to a nearly complete vanishing of fourfold Si. More generally, we show that the compressibility and density of noncrystalline solids can be accurately measured in simple optical experiments up to at least 110 GPa.

Automated summary

This study reported the first direct measurements of the refractive index of silica glass up to 145 GPa, and identified two major anomalies at around 10 and 40 GPa. The compressibility and density of noncrystalline solids were accurately measured in simple optical experiments up to at least 110 GPa.