Scalfi Laura, Coasne Benoît, Rotenberg Benjamin
Physicochimie des Électrolytes et Nanosystèmes Interfaciaux, Sorbonne Université, CNRS, 4 Place Jussieu, F-75005 Paris, France.
Laboratoire Interdisciplinaire de Physique, Université Grenoble Alpes, CNRS, LIPhy, 38000 Grenoble, France.
J Chem Phys. 2021 Mar 21;154(11):114711. doi: 10.1063/5.0044330.
The Gibbs-Thomson (GT) equation describes the shift of the crystallization temperature for a confined fluid with respect to the bulk as a function of pore size. While this century old relation is successfully used to analyze experiments, its derivations found in the literature often rely on nucleation theory arguments (i.e., kinetics instead of thermodynamics) or fail to state their assumptions, therefore leading to similar but different expressions. Here, we revisit the derivation of the GT equation to clarify the system definition, corresponding thermodynamic ensemble, and assumptions made along the way. We also discuss the role of the thermodynamic conditions in the external reservoir on the final result. We then turn to numerical simulations of a model system to compute independently the various terms entering in the GT equation and compare the predictions of the latter with the melting temperatures determined under confinement by means of hyper-parallel tempering grand canonical Monte Carlo simulations. We highlight some difficulties related to the sampling of crystallization under confinement in simulations. Overall, despite its limitations, the GT equation may provide an interesting alternative route to predict the melting temperature in large pores using molecular simulations to evaluate the relevant quantities entering in this equation. This approach could, for example, be used to investigate the nanoscale capillary freezing of ionic liquids recently observed experimentally between the tip of an atomic force microscope and a substrate.
吉布斯 - 汤姆逊（GT）方程描述了受限流体的结晶温度相对于本体的偏移与孔径的函数关系。虽然这个有着百年历史的关系式已成功用于分析实验，但文献中其推导往往依赖于成核理论观点（即动力学而非热力学），或者未阐明其假设，因此导致了相似但又不同的表达式。在此，我们重新审视GT方程的推导，以阐明系统定义、相应的热力学系综以及推导过程中所做的假设。我们还讨论了外部储库中的热力学条件对最终结果的作用。然后，我们转向一个模型系统的数值模拟，以独立计算GT方程中的各项，并将后者的预测结果与通过超平行回火巨正则蒙特卡罗模拟在受限条件下确定的熔化温度进行比较。我们强调了模拟中受限条件下结晶采样相关的一些困难。总体而言，尽管存在局限性，但GT方程可能为利用分子模拟预测大孔中的熔化温度提供一条有趣的替代途径，以评估该方程中涉及的相关量。例如，这种方法可用于研究最近在原子力显微镜尖端与基底之间通过实验观察到的离子液体的纳米级毛细管冻结现象。
