Domain structure, microscopic segregation and dynamics heterogeneity in alumina-silicate liquid

Abstract

We report molecular dynamics simulation for SiO2.Al2O3 liquid. The result shows that the system contains small TO-subnets (T is Si or Al) and two large ones consisting of 18 - 35% of total atoms. The average size of SiO-subnets is larger than AlO-subnets, and T-O-T angle distribution is quite different for three O types. The microscopic segregation occurs with formation of three distinct domains, whose number density is 57, 67 and 69 atom/nm3. Diffusion proceeds by collective movements without and with exchange of coordinated atoms. The exchange of coordinated atoms gives the major contribution. During 300 ps, there are Si-rich and Al-rich regions, where immobile and mobile O resides respectively. By examining atom's flow through a fixed cubic lattice we find that the system contains immobile and mobile regions where the atom flow significantly differs from each other. The dynamic heterogeneity is related to non-uniform spatial distribution of bond breaking-reforming.