Mohanakumar Shilpa, Kriegs Hartmut, Briels W J, Wiegand Simone
IBI-4:Biomacromolecular Systems and Processes, Forschungszentrum Jülich GmbH, D-52428 Jülich, Germany.
University of Twente, Computational Chemical Physics, Postbus 217, 7500 AE Enschede, The Netherlands.
Phys Chem Chem Phys. 2022 Nov 18;24(44):27380-27387. doi: 10.1039/d2cp04089a.
We investigate the thermodiffusive properties of aqueous solutions of sodium iodide, potassium iodide and lithium iodide, using thermal diffusion forced Rayleigh scattering in a concentration range of 0.5-4 mol kg of solvent, large enough to deal with associated salts, and a temperature range of 15 to 45 °C. All systems exhibit non-monotonic variations of the Soret coefficient with concentration, with a minimum at one mol kg of solvent in all three cases. We take this as an indication that the relevant length and energy scales are very similar in all cases. On this basis we develop an intuitive picture in which the relevant objects are the fully hydrated salt molecules, including all water molecules that behave differently from bulk water. Preliminary, somewhat sketchy calculations indicate that indeed Soret coefficients begin to rise beyond concentrations where the fully hydrated particles are randomly close packed. Indications are given as to why the model will fail at large concentrations.
我们利用热扩散强迫瑞利散射，在0.5 - 4 mol/kg溶剂的浓度范围内（该浓度范围足以处理缔合盐）以及15至45°C的温度范围内，研究了碘化钠、碘化钾和碘化锂水溶液的热扩散性质。所有体系的索雷特系数随浓度呈现非单调变化，在所有三种情况下，溶剂为1 mol/kg时出现最小值。我们认为这表明在所有情况下，相关的长度和能量尺度非常相似。在此基础上，我们构建了一个直观的图景，其中相关的对象是完全水合的盐分子，包括所有行为不同于体相水的水分子。初步的、有些粗略的计算表明，实际上索雷特系数在完全水合粒子随机密堆积的浓度以上开始上升。文中给出了该模型在高浓度下失效原因的相关说明。
