Origin of the emergent fragile-to-strong transition in supercooled water

Shi, Rui; Russo, John; Tanaka, Hajime

doi:10.1073/pnas.1807821115

Cited by 133 publications

(182 citation statements)

References 58 publications

(67 reference statements)

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“…The underlying assumption behind this relation is that the lifetime of locally favored structures is much shorter than the structural relaxation (or rotational relaxation) time of molecules (54,55). This has been recently confirmed for water models (56).…”

Section: Discussionmentioning

confidence: 82%

Link between molecular mobility and order parameter during liquid–liquid transition of a molecular liquid

Murata

Tanaka

2019

Proc. Natl. Acad. Sci. U.S.A.

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Liquid-liquid transition (LLT) is the transformation of one liquid to another via first-order phase transition. For example, LLT in a molecular liquid, triphenyl phosphite, is macroscopically the transformation from liquid I in a supercooled state to liquid II in a glassy state. Reflecting the transformation from the liquid to glassy state, the LLT is accompanied by considerable slowing down of overall molecular dynamics, but little is known about how this proceeds at a molecular level coupled with the evolution of the order parameter. We report such information by performing time-resolved simultaneous measurements of dielectric spectroscopy and phase contrast microscopy/Raman spectroscopy by using a dielectric cell with transparent electrodes. We find that the temporal change in molecular mobility crucially depends on whether LLT is nucleation growth type occurring in the metastable state or SD type occurring in the unstable state. Furthermore, our results suggest that the molecular mobility is controlled by the local order parameter: more specifically, the local activation energy of molecular rotation is controlled by the local fraction of locally favored structures formed in the liquid. Our study sheds light on the temporal change in the molecular dynamics during LLT and its link to the order parameter evolution.liquid-liquid transition | phase ordering dynamics | order parameter | local molecular dynamics | dielectric relaxation Significance Contrary to a common sense that a liquid state is unique for a pure system, there have been a number of indications for the presence of more than two liquid states. The transition between the liquid states is called "liquid-liquid transition." There has so far been little information on how local molecular dynamics changes during the transformation. Here, we reveal the correlation between the order parameter and molecular dynamics by real-time dielectric spectroscopy measurements during the transformation from liquid I to liquid II in a molecular liquid, triphenyl phosphite. Our results suggest that the local order parameter controls local dynamics. Our finding sheds light on the nature of liquid-liquid transition from a perspective of molecular-level dynamics.

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Section: Discussionmentioning

confidence: 82%

Link between molecular mobility and order parameter during liquid–liquid transition of a molecular liquid

Murata

Tanaka

2019

Proc. Natl. Acad. Sci. U.S.A.

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“…However, no divergence has ever been detected by measurements in supercooled, amorphous, and confined water, and instead a "fragileto-strong" (power-law to Arrhenius) transition is observed, which is further rationalized as a consequence of crossing the Widom line. 8,9,[21][22][23][24][25][26][27][28] In a recent study, 29 we have provided an alternative explanation of water's dynamic anomalies. According to this scenario, the observed fragile-to-strong transition is actually a crossover between two Arrhenius regimes, each corresponding to a different state (type of local structures) of water: a high-density ρ state at high temperatures and a low-density S state at low temperatures.…”

Section: Introductionmentioning

confidence: 89%

Common microscopic structural origin for water’s thermodynamic and dynamic anomalies

Shi

Russo

Tanaka

2018

The Journal of Chemical Physics

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123

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Water displays a vast array of unique properties, known as water's anomalies, whose origin remains subject to hot debate. Our aim in this article is to provide a unified microscopic physical picture of water's anomalies in terms of locally favored structures, encompassing both thermodynamic and dynamic anomalies, which are often attributed to different origins. We first identify locally favored structures via a microscopic structural descriptor that measures local translational order and provide direct evidence that they have a hierarchical impact on the anomalies. At each state point, the strength of thermodynamic anomalies is directly proportional to the amount of locally favored structures, while the dynamic properties of each molecule depend on the local structure surrounding both itself and its nearest neighbors. To incorporate this, we develop a novel hierarchical two-state model. We show by extensive simulations of two popular water models that both thermodynamic and kinetic anomalies can be almost perfectly explained by the temperature and pressure dependence of these local and non-local versions of the same structural descriptor, respectively. Moreover, our scenario makes three unique predictions in supercooled water, setting it apart from other scenarios: (1) Presence of an "Arrhenius-to-Arrhenius" crossover upon cooling, as the origin of the apparent "fragile-to-strong" transition; (2) maximum of dynamic heterogeneity around 20 K below the Widom line and far above the glass transition; (3) violation of the Stokes-Einstein-Debye relation at ∼2T g , rather than 1.2T g typical of normal glass-formers. These predictions are verified by recent measurement of water's diffusion at very low temperatures (point 1) and discoveries from our extensive simulations (points 2-3). We suggest that the same scenario may generally apply to water-like anomalies in liquids tending to form locally favored structures, including not only other important tetrahedral liquids such as silicon, germanium, and silica, but also metallic and chalcogenide liquids.

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“…Shaded regions indicate 95% confidence intervals. All data was obtained with the TIP4P/Ice water model at 240 K. ordered and disordered regions [21].…”

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confidence: 99%

Ice is born in low-mobility regions of supercooled liquid water

Fitzner

Sosso

Cox

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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SignificanceFrom intracellular freezing to cloud formation, the crystallization of water is ubiquitous and shapes life as we know it. A full comprehension of the ice nucleation process at the molecular scale remains elusive and we cannot predict where nucleation will occur. Using computational techniques we show that homogeneous nucleation in supercooled water happens in immobile liquid regions that emerge from heterogeneous dynamics. With this we link the topics of nucleation and dynamical heterogeneity and open ways to understand and control heterogeneous nucleation in solution, in confinement, or at interfaces via understanding their effects on liquid dynamics.

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Origin of the emergent fragile-to-strong transition in supercooled water

Cited by 133 publications

References 58 publications

Link between molecular mobility and order parameter during liquid–liquid transition of a molecular liquid

Link between molecular mobility and order parameter during liquid–liquid transition of a molecular liquid

Common microscopic structural origin for water’s thermodynamic and dynamic anomalies

Ice is born in low-mobility regions of supercooled liquid water

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