Alkali Halide Solutions under Thermal Gradients: Soret Coefficients and Heat Transfer Mechanisms
Alkali Halide Solutions under Thermal Gradients: Soret Coefficients and Heat Transfer Mechanisms
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DOI：
10.1021/jp403862x
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发表时间：
2013-07-11
影响因子：
3.3
通讯作者：
Bresme, Fernando
中科院分区：
文献类型：
--
作者：
Roemer, Frank;Wang, Zilin;Bresme, Fernando
我们报告了一个广泛的分析碱金属卤化物水溶液（Na+/K+-Cl-）的非平衡响应的热，梯度使用最先进的非平衡分子动力学模拟和热扩散强迫瑞利散射实验。通过Soret系数量化了热梯度和所得离子盐质量通量之间的耦合。在较宽的浓度范围内，Soret系数为10（-3）K ~（-1）。这些相对简单的解决方案具有非常丰富的行为。Soret系数在高温下（高于T，类似于315 K）随浓度降低，而在较低温度下则增加。与以前的实验一致，我们发现的迹象反转，索雷系数的NaCl和KCl的解决方案。我们使用原子非平衡分子动力学方法来计算Soret系数在广泛的条件下，并获得进一步的微观洞察力，在热传输机制上，Soret系数在水溶液中的行为：在这项工作中采用的模型再现Soret系数的大小，以及该系数与温度和盐浓度的一般依赖性。我们使用的计算机模拟作为一个微观的方法来建立，Soret的符号和大小之间的相关性，系数和离子溶剂化和氢键结构的解决方案。最后，我们报告了在离子溶液中的热传输的分析，通过量化溶液的热导率作为浓度的函数。模拟准确地再现了在实验中观察到的随着盐浓度的增加热导率的降低。提供了此行为的解释。
We report an extensive analysis of the non-equilibrium response of alkali halide aqueous solutions (Na+/K+-Cl-) to thermal, gradients using state of the art non-equilibrium molecular dynamics simulations and thermal diffusion forced Rayleigh scattering experiments. The coupling between the thermal gradient and the resulting ionic salt mass flux is quantified through the Soret coefficient. We find the Soret Coefficient is of the order of 10(-3) K-1 for a wide range of concentrations., These relatively simple solutions feature a very rich behavior. The Soret coefficient decreases with concentration at high temperatures (higher than T similar to 315 K), whereas it increases, at lower temperatures. In agreement with previous experiments, we find evidence for sign inversion in, the Soret coefficient of NaCl and KCl solutions. We use an atomistic non-equilibrium molecular: dynamics approach to compute the Soret coefficients in a wide range of conditions and to attain further microscopic insight, On the heat transport mechanism, the behavior Of the Soret coefficient in aqueous solutions: The models employed in this work reproduce the Magnitude of the Soret coefficient, and the general dependence of this coefficient with temperature and salt concentration. We use the computer simulations as a microscopic approach to establish,a correlation between the sign and magnitude of the Soret, coefficients and ionic solvation and hydrogen bond structure of the solutions. Finally, we report an analysis of heat transport in ionic solution by quantifying the solution thermal conductivity as a function of concentration. The simulations accurately reproduce the decrease of the thermal conductivity with increasing salt concentration that is observed in experiments. An explanation of this behavior is provided.