Zhang, H. (2022). The Fragile-to-Strong Crossover in Simulated Supercooled Water. Retrieved from https://doi.org/10.14418/wes01.2.376
Glass-forming liquids usually exhibit either “fragile” or “strong” behavior approaching the glass transition. In contrast, experimental and computational evidence indicates that supercooled water exhibits a novel “fragile-to-strong crossover” on cooling at low pressure, which is related to an expected liquid-liquid transition at higher pressure. We utilize molecular dynamics simulations to investigate how the fragile-to-strong crossover alters the nature of collective molecular rearrangements in water. We compare the results from two different models, TIP4P-2005 and ST2, to identify which results are likely to be general, and not an artifact of the model. We are able to identify thermodynamic and dynamic signatures of the fragile-to-strong crossover. Our data reveals that thermodynamic response functions approach asymptotic values around the crossover, in agreement with the proposed thermodynamic changes when the Widom line is crossed. Moreover, the fragile-to-strong crossover can be identified with the onset of landscape-dominated dynamics. Additionally, we found that structural changes on the molecular scale accompany the thermodynamic and dynamic changes.