A Direct Link between the Fragile-to-Strong Transition and Relaxation in Supercooled Liquids

It is known that both the fragile-to-strong (F−S) transition and relaxation processes occur in numerous supercooled liquids upon cooling toward the glass transition temperature. The key question is whether and how these two dynamic processes are correlated. Here, we show a direct link between the two processes for both metallic glass-forming liquids (MGFLs) with different fragilities and also for nonmetallic glass-forming liquids. By comparing the F−S transition extent parameter f with the parameter r that characterizes the competition between the α and the slow β relaxations, we have discovered a negative exponential connection between the two parameters of supercooled liquids. The finding indicates that the slow β relaxation plays a dominant role in the F−S transition. This work provides new insight into the microscopic mechanism of the F−S transition and creates a strong basis for predicting whether and to what extent the F−S transition occurs in supercooled liquids.