Qiu Yuqing, Molinero Valeria
Department of Chemistry , The University of Utah , Salt Lake City , Utah 84112-0580 , United States.
J Phys Chem Lett. 2018 Sep 6;9(17):5179-5182. doi: 10.1021/acs.jpclett.8b02244. Epub 2018 Aug 28.
Premelting of ice at temperatures below 0 °C is of fundamental importance for environmental processes. Various experimental techniques have been used to investigate the temperature at which liquid-like water first appears at the ice-vapor interface, reporting onset temperatures from -160 to -2 °C. The signals that identify liquid-like order at the ice-vapor interface in these studies, however, do not show a sharp initiation with temperature. That is at odds with the expected first-order nature of surface phase transitions, and consistent with recent large-scale molecular simulations that show the first premelted layer to be sparse and to develop continuously over a wide range of temperatures. Here we perform a thermodynamic analysis to elucidate the origin of the continuous formation of the first layer of liquid at the ice-vapor interface. We conclude that a negative value of the line tension of the ice-liquid-vapor three-phase contact line is responsible for the continuous character of the transition and the sparse nature of the liquid-like domains in the incomplete first layer.
在低于0°C的温度下冰的预融化对于环境过程至关重要。已经使用了各种实验技术来研究在冰-汽界面首次出现类液态水的温度，报道的起始温度范围为-160至-2°C。然而，在这些研究中用于识别冰-汽界面类液态有序的信号并没有随着温度的升高而急剧起始。这与表面相变预期的一级性质不一致，并且与最近的大规模分子模拟结果一致，该模拟结果表明第一个预融层是稀疏的，并且在很宽的温度范围内持续发展。在这里，我们进行了热力学分析，以阐明在冰-汽界面连续形成第一层液体的原因。我们得出结论，冰-液-汽三相接触线的线张力为负值是导致转变的连续性和不完全第一层中类液态域的稀疏性质的原因。
