含低密度无定形水低温相的过冷水溶液的液-液相变
Liquid-liquid transition in supercooled aqueous solution involving a low-temperature phase similar to low-density amorphous water
摘要：
在1960- 70年代发现的过冷水物理性质的惊人异常仍然没有完全理解，因此在理论家之间提供了争议的来源，并刺激实验学家和模拟器寻找穿透“结晶幕”的新方法，有效地屏蔽了问题的解决方案。最近，一个新的门的问题是打开显示，在理想的解决方案中，使用离子液体溶质，水的异常不破坏早期发现的普通盐和大多数分子溶质，而是被增强到沉淀一个明显的一级液-液转变的点。证据是在冷却过程中表观热容的峰值，在任何冰结晶的迹象出现之前，在重新加热过程中可以完全逆转。在这里，我们使用双振荡器红外光谱来定义这种现象的结构特征，使用类似的向下和向上扫描速率在量热研究。薄膜样品也允许慢扫描（1 K/min），其中过渡的宽度小于1 K，并且是完全可逆的。OH光谱在相变温度下不连续地变化，表明氢键结构的离散变化。光谱的变化表明，低温液体是更强的氢键和更少的无序相比，高温液体。低温液体的光谱基本上是在低密度无定形水中看到的。这种相似性表明，这里观察到的液-液转变也存在于纯净的过冷水中，为许多异常现象提供了统一的解释。
英文摘要：
The striking anomalies in physical properties of supercooled water that were discovered in the 1960-70s, remain incompletely understood and so provide both a source of controversy amongst theoreticians, and a stimulus to experimentalists and simulators to find new ways of penetrating the "crystallization curtain" that effectively shields the problem from solution. Recently a new door on the problem was opened by showing that, in ideal solutions, made using ionic liquid solutes, water anomalies are not destroyed as earlier found for common salt and most molecular solutes, but instead are enhanced to the point of precipitating an apparently first order liquid-liquid transition. The evidence was a spike in apparent heat capacity during cooling that could be fully reversed during reheating before any sign of ice crystallization appeared. Here, we use decoupled-oscillator infrared spectroscopy to define the structural character of this phenomenon using similar down and upscan rates as in the calorimetric study. Thin-film samples also permit slow scans (1 K/min) in which the transition has a width of less than 1 K, and is fully reversible. The OH spectrum changes discontinuously at the phase-transition temperature, indicating a discrete change in hydrogen-bond structure. The spectral changes show that the low-temperature liquid is more strongly hydrogen bonded and less disordered as compared to the high-temperature liquid. The spectrum of the low-temperature liquid is essentially that seen in low-density amorphous water. This similarity suggests that the liquid-liquid transition observed here also exists in neat undercooled water, providing a unified explanation for many of its anomalies.
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