The dynamic crossover in water does not require bulk water.
The dynamic crossover in water does not require bulk water.
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DOI：
10.1039/c2cp40703e
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发表时间：
2012-05
期刊：
影响因子：
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通讯作者：
D. Turton;C. Corsaro;David F Martin;F. Mallamace;K. Wynne
中科院分区：
文献类型：
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作者：
D. Turton;C. Corsaro;David F Martin;F. Mallamace;K. Wynne
水的许多异常性质可以通过调用第二临界点来解释，该临界点终止了液体中低密度和高密度非晶态之间的共存线。这一点的直接实验证据，以及相关的多晶液-液转变，是难以捉摸的，因为它是必要的液态水被冷却到低于其非晶成核温度。为了避免结晶，已经研究了低共熔LiCl溶液中的水，但是通常认为不能存在“本体”水。然而，最近的计算和实验研究观察到合作水合，在这种情况下，有可能存在足够的氢键合水，以保持水的基本特性。对于飞秒光学克尔效应和核磁共振测量，我们观察到在每种情况下的分数斯托克斯-爱因斯坦关系的动态交叉出现在220 K和250 K附近的证据分别。在玻璃状态下获得的光谱也证实了纯室温水报告的氢键模式的复杂性，并支持由于“虫洞”结构的异常扩散的预测。
Many of the anomalous properties of water may be explained by invoking a second critical point that terminates the coexistence line between the low- and high-density amorphous states in the liquid. Direct experimental evidence of this point, and the associated polyamorphic liquid-liquid transition, is elusive as it is necessary for liquid water to be cooled below its homogeneous-nucleation temperature. To avoid crystallization, water in the eutectic LiCl solution has been studied but then it is generally considered that "bulk" water cannot be present. However, recent computational and experimental studies observe cooperative hydration in which case it is possible that sufficient hydrogen-bonded water is present for the essential characteristics of water to be preserved. For femtosecond optical Kerr-effect and nuclear magnetic resonance measurements, we observe in each case a fractional Stokes-Einstein relation with evidence of the dynamic crossover appearing near 220 K and 250 K respectively. Spectra obtained in the glass state also confirm the complex nature of the hydrogen-bonding modes reported for neat room-temperature water and support predictions of anomalous diffusion due to "worm-hole" structure.