Insight into dynamics and microstructure of aluminum-silicate melts from molecular dynamics simulation

We have conducted a systematic analysis on dynamics and structure of aluminum-silicate melt at various pressures and at 3500 K. Firstly, the analysis with respect to network structure units reveals that the melt contains separate Si-O and Al-O subnets which evidences the micro-segregation of the liquid. We propose a model of solid-like particle to interpret the diffusivity for three types of atom. Secondly, from the analysis on the sets, immobile, mobile and random atoms we reveal the dynamics heterogeneity (DH) in the melt. Moreover the simulation also shows a clear correlation between DH and structural heterogeneity. Finally, the analysis with respect to O-simplex and T-simplex provides a new view on the structure of the melt. It was shown that there are not only T-clusters with one atom that form a simple network structure, but instead the melt contains a number of T-cluster with numerous atoms. The structure heterogeneity of silicate melt concerns two aspects: T-clusters and O-simplexes which contain extremely large number of atom. (C) 2017 Elsevier B.V. All rights reserved.