Caupin Frédéric, Anisimov Mikhail A
Institut Lumière Matière, Université Claude Bernard Lyon 1, CNRS, Université de Lyon, F-69622, Villeurbanne, France.
Department of Chemical and Biomolecular Engineering and Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA.
J Chem Phys. 2019 Jul 21;151(3):034503. doi: 10.1063/1.5100228.
We have applied a two-structure approach to the description of the thermodynamic properties of supercooled and stretched water, metastable toward vapor, ice, or both, by incorporating the stability limit of liquid with respect to vapor at negative pressures. In addition to the properties of water considered in previous studies, we include new data recently obtained in deeply supercooled and stretched regions. Our model reproduces the experimentally observed anomalies in metastable water up to 400 MPa and down to -140 MPa, and can provide a physically based extrapolation in regions where no measurements are available yet. Moreover, we are able to elucidate the thermodynamic nature of the alternative "states" of liquid water, namely, high-temperature denser water (state A) and "mother-of-ice" lighter water (state B). Based on the internal consistency of the described anomalies and new data on the isothermal compressibility, we exclude the critical-point-free scenario in which the first-order liquid-liquid transition line would continue into the stretched liquid state (doubly metastable) crossing the vapor-liquid spinodal. A "singularity-free" scenario remains an option for explaining supercooled water's anomalies within the framework of two-state thermodynamics; however, the extreme case of the singularity-free scenario, ideal mixing of A and B, seems improbable. We have also clarified the concept of fast interconversion of alternative states in supercooled water as a phenomenological representation of distribution of short-ranged local structures.
我们采用了一种双结构方法来描述过冷水和拉伸水的热力学性质，这些水对于蒸汽、冰或两者而言是亚稳态的，该方法通过纳入液体在负压下相对于蒸汽的稳定性极限来实现。除了先前研究中考虑的水的性质外，我们还纳入了最近在深度过冷和拉伸区域获得的新数据。我们的模型再现了在高达400MPa和低至 -140MPa的亚稳态水中实验观察到的异常现象，并且可以在尚无测量数据的区域提供基于物理的外推。此外，我们能够阐明液态水的替代“状态”的热力学性质，即高温高密度水（A态）和“冰之母”低密度水（B态）。基于所描述的异常现象的内部一致性以及关于等温压缩率的新数据，我们排除了无临界点的情况，即在这种情况下，一级液 - 液转变线将继续延伸到拉伸液态（双亚稳态）并穿过气 - 液旋节线。在双态热力学框架内，“无奇点”情况仍然是解释过冷水异常现象的一种选择；然而，无奇点情况的极端情况，即A和B的理想混合，似乎不太可能。我们还澄清了过冷水中替代状态快速相互转换的概念，将其作为短程局部结构分布的一种现象学表示。
