Molecular Dynamics Study on the Effect of SiO2/Al2O3 Mass Ratio on the Structural Properties and Viscosity of Molten Fused Red Mud

In this study, molecular dynamics simulation was used to study the effect of SiO2/Al2O3 mass ratio on the structural properties and viscosity of molten fused red mud. The stability of various T–O bonds in the melt was elucidated by analyzing the bond angle and coordination number; the degree of polymerization, and the stability of the melt were explored by analyzing the number of T–O–T bridging oxygen (BO) and the distribution of QSin and QAln of [SiO4]4− as well as that of QSin and QAln of [AlO4]5−; the self-diffusion coefficient of each atom was determined by mean square displacement (MSD) analysis; and the trend of the melt viscosity was analyzed according to the relationship between diffusion and viscosity. The results show that as the ratio of SiO2/Al2O3 increases, the viscosity of molten fused red mud first increases, then decreases, and finally increases. This is because Ti4 and Fe3+ combine with O2− to form [TiO6]8− octahedron and [FeO4]5− tetrahedra, which increase the degree of depolymerization of the melt.