Molecular simulations of silicate melts doped with sulphur and nitrogen

This work presents ab initio molecular dynamics (MD) models of the sulphur and nitrogen bearing silicate melts. Small concentrations of volatile admixtures strongly influence the physical and chemical properties of both natural and industrial silicate materials, e.g. the solubility of gases in melts is of great importance in geochemistry (degassing of magma) as well as glass technology (fining of glass). The valency and bonding of sulphur and nitrogen are affected by the oxidation–reduction (redox) state of molten glass. The present work investigates the structure and properties of the soda–lime–silica melts containing sulphur or nitrogen with respect to the redox conditions of the melt. The coordinations of sulphur and nitrogen species were analyzed and systematic trends with respect to redox were found. Moreover, the reaction trajectories of individual molecular species were identified. Sulphur was found to readily interact with the silicate network by forming unstable transition complexes on the pathway from SO2 to SO42−. On the other hand, the nitrogen oxides were much more indifferent towards the silicate melt.