Hellmuth Olaf, Schmelzer Jürn W P, Feistel Rainer
Leibniz Institute for Tropospheric Research (TROPOS), Permoserstraße 15, D-04318 Leipzig, Germany.
Institute of Physics, University of Rostock, Albert-Einstein-Straße 23-25, D-18059 Rostock, Germany.
Entropy (Basel). 2019 Dec 30;22(1):50. doi: 10.3390/e22010050.
A recently developed thermodynamic theory for the determination of the driving force of crystallization and the crystal-melt surface tension is applied to the ice-water system employing the new Thermodynamic Equation of Seawater TEOS-10. The deviations of approximative formulations of the driving force and the surface tension from the exact reference properties are quantified, showing that the proposed simplifications are applicable for low to moderate undercooling and pressure differences to the respective equilibrium state of water. The TEOS-10-based predictions of the ice crystallization rate revealed pressure-induced deceleration of ice nucleation with an increasing pressure, and acceleration of ice nucleation by pressure decrease. This result is in, at least, qualitative agreement with laboratory experiments and computer simulations. Both the temperature and pressure dependencies of the ice-water surface tension were found to be in line with the le Chatelier-Braun principle, in that the surface tension decreases upon increasing degree of metastability of water (by decreasing temperature and pressure), which favors nucleation to move the system back to a stable state. The reason for this behavior is discussed. Finally, the Kauzmann temperature of the ice-water system was found to amount T K = 116 K , which is far below the temperature of homogeneous freezing. The Kauzmann pressure was found to amount to p K = - 212 MPa , suggesting favor of homogeneous freezing on exerting a negative pressure on the liquid. In terms of thermodynamic properties entering the theory, the reason for the negative Kauzmann pressure is the higher mass density of water in comparison to ice at the melting point.
一种最近开发的用于确定结晶驱动力和晶体 - 熔体表面张力的热力学理论，应用于采用新的海水热力学方程TEOS - 10的冰水系统。对驱动力和表面张力的近似公式与精确参考性质的偏差进行了量化，结果表明所提出的简化方法适用于低至中等过冷度以及与水的各自平衡状态的压力差情况。基于TEOS - 10对冰结晶速率的预测显示，随着压力增加，压力会导致冰核形成减速，而压力降低则会加速冰核形成。这一结果至少在定性上与实验室实验和计算机模拟一致。发现冰水表面张力的温度和压力依赖性均符合勒夏特列 - 布劳恩原理，即随着水的亚稳度增加（通过降低温度和压力），表面张力会降低，这有利于成核以使系统回到稳定状态。文中讨论了这种行为的原因。最后，发现冰水系统的考兹曼温度为TK = 116 K，远低于均匀冻结温度。考兹曼压力为pK = - 212 MPa，这表明对液体施加负压有利于均匀冻结。就该理论所涉及的热力学性质而言，考兹曼压力为负的原因是在熔点时水的质量密度高于冰。
