Vitreous silica distends in helium gas: acoustic vs. static compressibilities

TL;DR

This study investigates how helium gas affects the elastic properties of vitreous silica, revealing that helium suppresses certain anomalies and continues to incorporate into the structure under high pressure.

Contribution

It demonstrates that helium incorporation influences the elastic anomalies in vitreous silica and provides new insights into the relationship between helium diffusion and structural void collapse.

Findings

Helium suppresses the maximum in compressibility pressure dependence.

Significant helium incorporation persists at 6 GPa.

Elastic anomaly linked to collapse of interstitial voids.

Abstract

Sound velocities of vitreous silica are measured under He compression in the pressure range 0-6 GPa by Brillouin light scattering. It is found that the well-known anomalous maximum in the pressure dependence of the compressibility is suppressed by He incorporation into the silica network. This shows that the elastic anomaly relates to the collapse of the largest interstitial voids in the structure. The huge difference between the static and the acoustic compressibilities indicates that the amount of incorporated helium still increases at 6 GPa.