Chemically Driven Nano-Elastic Heterogeneities Control Fragility in Volcanic Melts

Here, the nanoscale structural drivers of the mechanical behavior of volcanic glasses  are explored. The study spans a compositional series ranging from basalt to rhyolite, encompassing also technical glass-forming melts. Using a granular-medium framework, the vibrational and physical properties of synthetic silicate glass-forming melts are characterized. From these, this study quantifies the correlation length (ξ) and microscopic free volume (V_c), two parameters linked to the internal structural heterogeneity of the glass network. This study finds that both ξ and V_c systematically increase with silica content and show strong inverse correlations with elastic moduli and the melt fragility, highlighting how variations in medium-range order affect the elastic and viscous response of the melt. These results provide a quantitative framework to connect compositional changes with rheological behavior, offering new perspectives on how nanoscale structural features contribute to the mechanical evolution of silicate melts.