Structural properties of liquid aluminosilicate with varying Al₂O₃/SiO₂ ratios: Insight from analysis and visualization of molecular dynamics data

Molecular dynamics (MD) simulations and visualizations were explored to investigate the changes in structure of liquid aluminosilicates. The models were constructed for four compositions with varying Al₂O₃/SiO₂ ratio. The local structure and network topology was analyzed through the pair of radial distribution functions, bond angle, bond length and coordination number distributions. The results showed that the structure of aluminosilicates mainly consists of the basic structural units TO${}_y$ (T is Al or Si; y = 3, 4, 5). Two adjacent units TO${}_y$ are linked to each other through common oxygen atoms and form continuous random network of basic structural units TO${}_y$. The bond statistics (corner-, edge- and face- sharing) between two adjacent TO${}_y$ units are investigated in detail. The self-diffusion coefficients for three atomic types are affected by the degree of polymerization (DOP) of network characterized by the proportions of nonbridging oxygen (NBO) and Q${}^n$ species in the system. It was found that Q⁴ and Q³ tetrahedral species (tetrahedron with four and three bridging oxygens, respectively) decreases, while Q⁰ (with four nonbridging oxygen) increase with increasing Al₂O₃/SiO₂ molar ratio, suggesting that a less polymerized network was formed. The structural and dynamical heterogeneities, micro-phase separation and liquid–liquid phase transition are also discussed in this work.