Analysis for characterizing the structure and dynamics in sodium di-silicate liquid

The analysis on dynamics and structure is carried out for sodium di-silicate melt. The simulation shows two moving types: the correlation motion for oxygen, silicon and free motion for sodium. The dynamics heterogeneity (DH) is found for oxygen and silicon. We reveal that the correlation motion type is responsible for DH and positive pressure dependence of diffusivity. The structural heterogeneity of the melt was analyzed by void-simplex, cation-simplex and oxygen-simplex. The densification of the melt is realized by decrease in the radius and change in the number of void-simplex. We show that a number of large interstitial site for oxygen and cation present in the liquid. The large site for oxygen plays a role as the cage capturing the oxygen atom for long time. Furthermore, we found a number of negative-charged and positive-charged clusters which evidence the heterogeneity in chemical composition and local environment. The large positive-charged cluster is found to be a diffusion pathway for sodium. •Two moving types for Si, O and Na are proposed.•The correlation motion type is shown to be responsible for DH and positive pressure dependence of diffusivity.•The simulation reveals a number of large interstitial site for oxygen and diffusion pathway for sodium.•The liquid exhibits the heterogeneity in chemical composition and local environment.