Ionic self-diffusion and the glass transition anomaly in aluminosilicates

The glass transition temperature (T-g) is the temperature after which a supercooled liquid undergoes a dynamical arrest. Usually, glass network modifiers (e.g., Na2O) affect the behavior ofT(g). However, in aluminosilicate glasses, the effect of different modifiers onT(g)is still unclear and shows an anomalous behavior. Here, based on molecular dynamics simulations, we show thatT(g)decreases with increasing charge balancing cation field strength (FS) in the aluminosilicate glasses, which is an anomalous behavior as compared to other oxide glasses. The results show that the origins of this anomaly come from the dynamics of the supercooled liquid aboveT(g), which in turn is correlated to pair excess entropy. Our results deepen our understanding of the effect of different modifiers on the properties of the aluminosilicate glasses.