A structure model for phase separated fluoroaluminosilicate glass system by molecular dynamic simulations

Oxyfluoride glass and glass ceramics have been widely used in optical devices with Ln3+ doping. Especially, fluoride phase separation is considered as the initial stage of nanocrystallization that can help to realize the controllable crystallization and also provide the low phonon energy environment in oxyfluoride glass. Therefore, a structure model to describe this phase separated glass system is in great help for designing optical materials with high luminescence. In this study, large-scale molecular dynamics (MD) simulations were performed to understand the structural heterogeneity and make attempt to propose a structure model for fluoroaluminosilicate glass. The simulation results reveal immiscible behaviors of the fluoroaluminosilicate glass that separate into fluoride-rich phase and aluminosilicate-rich residual matrix, which have structural features analogous to fluoride and aluminosilicate glass, respectively. Besides, Al3+ plays an essential role to inter-connect oxygen and fluorine ions on the oxide-fluoride phase interface, maintaining the stability of the glass system.