Consistent description of ion-specificity in bulk and at interfaces by solvent implicit simulations and mean-field theory
Consistent description of ion-specificity in bulk and at interfaces by solvent implicit simulations and mean-field theory
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DOI：
10.1063/5.0016103
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发表时间：
2020-07-21
影响因子：
4.4
通讯作者：
Netz, Roland R.
中科院分区：
文献类型：
--
作者：
dos Santos, Alexandre P.;Uematsu, Yuki;Netz, Roland R.
用溶剂隐式蒙特卡罗(MC)模拟和平均场理论预测了NaF、NaC l、NaI、KF、KCl和KI溶液的活度系数和超额界面张力，在整个实验可用浓度范围内与实验数据符合得很好。通过对实验活度系数数据的拟合，得到了溶剂隐式模拟模型的有效离子直径。高盐浓度下的实验活度系数只有在计入离子浓度依赖的介电常数递减的情况下才能重现。介电常数与单离子溶剂化自由能对活度系数的贡献是显著的，并被包括在内。为了解释盐溶液中离子特有的过量界面张力，除了非理想溶液效应和依赖于盐浓度的介电损耗外，还必须考虑离子特有的离子界面相互作用。这种离子-界面相互作用是在介电镜像电荷排斥的基础上起作用的，它被模拟为盒势，比离子半径远得多，并且对除碘以外的所有离子都是排斥的，这与以前的发现和论点是一致的。通过比较考虑或不考虑非理想溶液行为、介电衰减效应和离子-界面相互作用势的不同模型，我们演示了离子专有效应如何相互耦合和部分补偿。我们的MC模拟正确地包括了离子关联和界面介电镜像电荷排斥，用于确定可用于改进的Poisson-Boltzmann理论的有效离子-表面相互作用势。
Solvent-implicit Monte Carlo (MC) simulations and mean-field theory are used to predict activity coefficients and excess interfacial tensions for NaF, NaCl, NaI, KF, KCl, and KI solutions in good agreement with experimental data over the entire experimentally available concentration range. The effective ionic diameters of the solvent-implicit simulation model are obtained by fits to experimental activity coefficient data. The experimental activity coefficients at high salt concentrations are only reproduced if the ion-specific concentration-dependent decrement of the dielectric constant is included. The dielectric-constant dependent contribution of the single-ion solvation free energy to the activity coefficient is significant and is included. To account for the ion-specific excess interfacial tension of salt solutions, in addition to non-ideal solution effects and the salt-concentration-dependent dielectric decrement, an ion-specific ion-interface interaction must be included. This ion-interface interaction, which acts in addition to the dielectric image-charge repulsion, is modeled as a box potential, is considerably more long-ranged than the ion radius, and is repulsive for all ions considered except iodide, in agreement with previous findings and arguments. By comparing different models that include or exclude bulk non-ideal solution behavior, dielectric decrement effects, and ion-interface interaction potentials, we demonstrate how bulk and interfacial ion-specific effects couple and partially compensate each other. Our MC simulations, which correctly include ionic correlations and interfacial dielectric image-charge repulsion, are used to determine effective ion-surface interaction potentials that can be used in a modified Poisson-Boltzmann theory.