Atomistic understanding of the network dilation anomaly in ion-exchanged glass

► Network dilation coefficient describes the amount of strain per unit change in alkali. ► Network dilation of ion-exchanged glass is less than that of as-melted glasses. ► Molecular dynamics simulations reveal the atomic origin of the network dilation anomaly. ► Network dilation anomaly due to K+ coordination in as-melted vs. ion-exchanged glasses.