液体中的热泳现象及其与平衡温度的关系
Thermophoresis in Liquids and its Connection to Equilibrium Quantities
摘要：
热泳是热力学系统中粒子沿温度梯度运动的过程。尽管已经研究了150多年，但既没有液体中热泳的完整理论描述，也没有Soret系数，Soret平衡的定量测量。最近的研究将它的性质与系统的平衡性质联系起来，即过量焓和过量熵，而对于哪一个更准确地描述Soret系数以及它是否可以使用这些量来表示仍然存在争议。在这项工作中，我提出了一个理论描述这两种情况下的密度分析的基础上，通过布朗运动和动态密度泛函理论，我假设局部平衡。解释的布朗随机微分方程（ESTA）作为伊藤或Stratonovich ESTA的结果的密度的影响。我认为，Soret系数成正比的过剩焓连接到一个系统的热梯度以下的状态方程。此外，我推导出，玻尔兹曼分布定律的外部潜力并不适用于系统的热梯度，但必须由一个更一般的量。理论预测，因此测试通过BD模拟，其中几个系统被示出遵循其状态方程。在玩具模型溶剂中的溶质的Soret系数示出成比例的溶质的平衡溶剂化焓。我进一步尝试通过SPC/E水中惰性气体溶质的分子动力学模拟来验证理论推导。虽然Soret平衡SPC/E水密度遵循其状态方程，但Soret系数和Soret平衡溶质密度都不需要与任何理论预测一致。
英文摘要：
Thermophoresis is the process of particles moving along a temperature gradient in thermodynamic systems. Even though it has been studied for over 150 years, there is neither a complete theoretical description of thermophoresis in liquids nor of the Soret coefficient, the quantifiying measure of the Soret equilibrium. Recent studies connect its nature to equilibrium properties of the system, namely the excess enthalpy and the excess entropy, while there is still a debate over which of both describes the Soret coefficient more accurately and whether it can even be represented using those quantities. In this work I present a theoretical description for both cases based on density analysis by means of Brownian motion and dynamical density functional theory, where I assume local equilibrium. The interpretation of the Brownian stochastic differential equation (SDE) as an Ito or Stratonovich SDE is shown to have an influence on the outcome of the density. I argue that a Soret coefficient proportional to the excess enthalpy is connected to a system in a thermal gradient following its equation of state. Furthermore, I derive that the Boltzmann distribution law for external potentials does not hold for systems in thermal gradients but has to be replaced by a more general quantity. The theoretical predictions are consequently tested by means of BD simulations, where several systems are shown to follow their equation of state. The Soret coefficient of a solute in a toy model solvent is shown to be proportional to the solute's equilibrium solvation enthalpy. I further attempt to verify the theoretic derivations by means of MD simulations of noble gas solutes in SPC/E water. While the Soret equilibrium SPC/E water density follows its equation of state, neither Soret coefficient nor Soret equilibrium solute densitie entail a coherent agreement with any of the theoretical predictions.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
