Glassy Dynamics\nand Local Crystalline Order in Two-Dimensional\nAmorphous Silica

We reassess the modeling of amorphous silica bilayers\nas a 2D classical\nsystem whose particles interact with an effective pairwise potential.\nWe show that it is possible to reparametrize the potential developed\nby Roy, Heyde, and Heuer to quantitatively match the structural details\nof the experimental samples. We then study the glassy dynamics of\nthe reparametrized model at low temperatures. Using appropriate cage-relative\ncorrelation functions, which suppress the effect of Mermin–Wagner\nfluctuations, we highlight the presence of two well-defined Arrhenius\nregimes separated by a narrow crossover region, which we connect to\nthe thermodynamic anomalies and changes in the local structure. We\nfind that the bond-orientational order grows steadily below the crossover\ntemperature and is associated with transient crystalline domains of\nnanometric size. These findings raise fundamental questions about\nthe nature of the glass structure in two dimensions and provide guidelines\nto interpret the experimental data.