Boström M, Ninham B W
Department of Physics and Measurement Technology, Linköping University, SE-581 83 Linköping, Sweden.
Langmuir. 2004 Aug 31;20(18):7569-74. doi: 10.1021/la049446+.
The role for many-body dipolar (dispersion) potentials in ion-solvent and ion-solvent-interface interactions is explored. Such many-body potentials, accessible in principle from measured dielectric data, are necessary in accounting for Hofmeister specific ion effects. Dispersion self-energy is the quantum electrodynamic analogue of the Born electrostatic self-energy of an ion. We here describe calculations of dispersion self-free energies of four different anions (OH-, Cl-, Br-, and I-) that take finite ion size into account. Three different examples of self-free energy calculations are presented. These are the self-free energy of transfer of an ion to bulk solution, which influences solubility; the dispersion potential acting between one ion and an air-water interface (important for surface tension calculations); and the dispersion potential acting between two ions (relevant to activity coefficient calculations). To illustrate the importance of dispersion self-free energies, we compare the Born and dispersion contributions to the free energy of ion transfer from water to air (oil). We have also calculated the change in interfacial tension with added salt for air (oil)-water interfaces. A new model is used that includes dispersion potentials acting on the ions near the interface, image potentials, and ions of finite size that are allowed to spill over the solution-air interface. It is shown that interfacial free energies require a knowledge of solvent profiles at the interface.
探索了多体偶极（色散）势在离子 - 溶剂和离子 - 溶剂界面相互作用中的作用。这种原则上可从测量的介电数据获得的多体势，对于解释霍夫迈斯特特定离子效应是必要的。色散自能是离子的玻恩静电自能的量子电动力学类似物。我们在此描述了考虑有限离子尺寸的四种不同阴离子（OH⁻、Cl⁻、Br⁻和I⁻）的色散自自由能的计算。给出了三个不同的自自由能计算示例。这些是离子转移到本体溶液中的自自由能，它影响溶解度；一个离子与气 - 水界面之间的色散势（对表面张力计算很重要）；以及两个离子之间的色散势（与活度系数计算相关）。为了说明色散自自由能的重要性，我们比较了玻恩贡献和色散贡献对离子从水转移到空气（油）的自由能的影响。我们还计算了添加盐时气（油） - 水界面的界面张力变化。使用了一个新模型，该模型包括作用在界面附近离子上的色散势、镜像势以及允许溢出溶液 - 空气界面的有限尺寸离子。结果表明，界面自由能需要了解界面处的溶剂分布。
