Microscopic and thermodynamic origins of volume relaxation in soda-lime aluminosilicate glasses below the glass transition temperature

The microscopic and thermodynamic features of structural relaxation below the glass transition temperature are still major unsolved problems in the field of glass science. In this study, we used both experimental and theoretical approaches to elucidate the role of non-bridging oxygens in the volume relaxation of soda-lime aluminosilicate glasses below the glass transition temperature. Both approaches yielded similar trends, with greater shrinkage observed for glasses with a higher number of non-bridging oxygens. Based on our findings, we proposed and validated a theoretical equation for determining the volume relaxation time. Molecular dynamics simulations also suggested that volume relaxation is affected by the stericity of the rings in the glass network.