Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, USA.
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 Feb 14;150(6):064503. doi: 10.1063/1.5078446.
Water exhibits anomalous behavior in its supercooled region. A widely invoked hypothesis to explain supercooled water's thermodynamic anomalies is the existence of a metastable liquid-liquid transition terminating at a critical point. In this work, we analyze previously published and new simulation results for three commonly used molecular water models (ST2, TIP4P/2005, and TIP5P) that support the existence of the metastable liquid-liquid transition. We demonstrate that a corresponding-states-like rescaling of pressure and temperature results in a significant degree of universality in the pattern of extrema loci of the density, isothermal compressibility, and isobaric heat capacity. We also report, for the first time, an intriguing correlation between the location of the liquid-liquid critical point, the rescaled locus of density extrema, and the stability limit of the liquid state with respect to the vapor. A similar correlation is observed for two theoretical models that also exhibit a second (liquid-liquid) critical point, namely, the van der Waals and lattice-gas "two-structure" models. This new correlation is used to explore the stability limit of the liquid state in simultaneously supercooled and stretched water.
水在过冷区域表现出异常行为。为了解释过冷水的热力学异常现象，人们广泛提出了一种假说，即存在亚稳的液-液相变，其终止于临界点。在这项工作中，我们分析了三个常用的水分子模型（ST2、TIP4P/2005 和 TIP5P）的先前发表和新的模拟结果，这些结果支持亚稳的液-液相变的存在。我们证明，对压力和温度进行相似状态缩放会导致密度、等温压缩率和等压热容极值轨迹的模式具有显著的普适性。我们还首次报告了液-液相变临界点的位置、密度极值的缩放轨迹与液体相对于蒸汽的稳定性极限之间的有趣相关性。对于两个也表现出第二个（液-液）临界点的理论模型，即范德华和晶格气体“双结构”模型，也观察到了类似的相关性。这种新的相关性被用于探索同时过冷和拉伸的水中液体状态的稳定性极限。
