Anomalies in bulk supercooled water at negative pressure
Anomalies in bulk supercooled water at negative pressure
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DOI：
10.1073/pnas.1323366111
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发表时间：
2014-06-03
影响因子：
11.1
通讯作者：
Caupin, Frederic
中科院分区：
文献类型：
--
作者：
Pallares, Gael;Azouzi, Mouna El Mekki;Caupin, Frederic
水异常仍然无法解释。在过冷液体中，许多量，如热容和等温压缩率kappa(T)，都有很大的增加。问题是这些量是否发散，或者它们是否达到最大值。答案是我们理解水异常的关键。然而，由于结晶总是在达到极值之前发生，因此在实验中一直难以捉摸。在这里，我们报告了在相图中很少被探索的区域中水的声速的测量，在那里水既过冷又处于负压。我们发现了几个异常：绝热压缩率和声速的非单调密度依赖的最大值，与状态方程的标准外推相反。这使人想起超临界流体的行为。为了支持这一解释，我们用2005年修订的四点可转移相互作用势进行了模拟。模拟和实验结果在定量上接近一致，表明在kappa(T) （LM kappa(T)）中存在一条极大值线。这个LM kappa(T)可能是水的密度最大值线的热力学结果[Sastry S， Debenedetti PG, Sciortino F, Stanley HE (1996) Phys Rev E 53: 6144-6154]，或者是从终止液-液转变的临界点发出的[Sciortino F， Poole PH, Essmann U, Stanley HE (1997) Phys Rev E 55: 727-737]。在正压下，LM kappa(T)由于位于均匀结晶线之外的“无人区”而没有被观察到。我们建议LM kappa(T)在负压下从无人区出现。
Water anomalies still defy explanation. In the supercooled liquid, many quantities, for example heat capacity and isothermal compressibility kappa(T), show a large increase. The question arises if these quantities diverge, or if they go through a maximum. The answer is key to our understanding of water anomalies. However, it has remained elusive in experiments because crystallization always occurred before any extremum is reached. Here we report measurements of the sound velocity of water in a scarcely explored region of the phase diagram, where water is both supercooled and at negative pressure. We find several anomalies: maxima in the adiabatic compressibility and nonmonotonic density dependence of the sound velocity, in contrast with a standard extrapolation of the equation of state. This is reminiscent of the behavior of super-critical fluids. To support this interpretation, we have performed simulations with the 2005 revision of the transferable interaction potential with four points. Simulations and experiments are in near-quantitative agreement, suggesting the existence of a line of maxima in kappa(T) (LM kappa(T)). This LM kappa(T) could either be the thermodynamic consequence of the line of density maxima of water [Sastry S, Debenedetti PG, Sciortino F, Stanley HE (1996) Phys Rev E 53: 6144-6154], or emanate from a critical point terminating a liquid-liquid transition [Sciortino F, Poole PH, Essmann U, Stanley HE (1997) Phys Rev E 55: 727-737]. At positive pressure, the LM kappa(T) has escaped observation because it lies in the "no man's land" beyond the homogeneous crystallization line. We propose that the LM kappa(T) emerges from the no man's land at negative pressure.