Biddle John W, Holten Vincent, Anisimov Mikhail A
Institute for Physical Science and Technology and Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, Maryland 20742, USA.
J Chem Phys. 2014 Aug 21;141(7):074504. doi: 10.1063/1.4892972.
A popular hypothesis that explains the anomalies of supercooled water is the existence of a metastable liquid-liquid transition hidden below the line of homogeneous nucleation. If this transition exists and if it is terminated by a critical point, the addition of a solute should generate a line of liquid-liquid critical points emanating from the critical point of pure metastable water. We have analyzed thermodynamic consequences of this scenario. In particular, we consider the behavior of two systems, H2O-NaCl and H2O-glycerol. We find the behavior of the heat capacity in supercooled aqueous solutions of NaCl, as reported by Archer and Carter [J. Phys. Chem. B 104, 8563 (2000)], to be consistent with the presence of the metastable liquid-liquid transition. We elucidate the non-conserved nature of the order parameter (extent of "reaction" between two alternative structures of water) and the consequences of its coupling with conserved properties (density and concentration). We also show how the shape of the critical line in a solution controls the difference in concentration of the coexisting liquid phases.
一种解释过冷水异常现象的流行假说是，存在一种隐藏在均匀成核线以下的亚稳液-液转变。如果这种转变存在，并且如果它由一个临界点终止，那么添加溶质应该会产生一条从纯亚稳水的临界点发出的液-液临界点线。我们分析了这种情况的热力学后果。特别地，我们考虑了两个系统，即H₂O-NaCl和H₂O-甘油。我们发现，正如阿彻和卡特[《物理化学杂志B》104, 8563 (2000)]所报道的，NaCl过冷水溶液中热容的行为与亚稳液-液转变的存在是一致的。我们阐明了序参量（水的两种替代结构之间“反应”的程度）的非守恒性质及其与守恒性质（密度和浓度）耦合的后果。我们还展示了溶液中临界线的形状如何控制共存液相浓度的差异。
