Many applications of ionic liquids involve their mixtures with neutral molecular solvents. The chemical physics of these high-concentration electrolytes, in particular at interfaces, still holds many challenges. In this contribution we begin to unravel the relationship between measurements of structural (‘solvation’) forces in mixtures of ionic liquid with polar solvent and the corresponding structure determined by molecular dynamics simulations of the same mixtures. In order to make the quantitative link between experiments with mica surfaces and simulations with fixed-charge surfaces, we present an experimental procedure for determining the effective surface charge on mica in ionic liquid. We find that a structural cross-over recently inferred from force measurements appears to be supported by the simulations: at the cross-over, the charge-oscillatory structure switches to charge-monotonic, and solvent layering becomes dominant. Finally, we map out a phase diagram in composition-surface charge space delineating regions of charge-oscillatory interfacial structure and regions of charge-monotonic decay. We note that these features of structure and oscillatory forces are distinct from (acting simultaneously with) the recently reported longer range monotonic forces arising from anomalously long bulk screening lengths in high-concentration electrolytes.

中文翻译：

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离子液体与极性溶剂的混合物中的界面结构和结构力

离子液体的许多应用涉及它们与中性分子溶剂的混合物。这些高浓度电解质的化学物理，特别是在界面处，仍然面临许多挑战。在这一贡献中，我们开始揭示离子液体与极性溶剂的混合物中结构（“溶剂化”）力的测量值与通过相同混合物的分子动力学模拟确定的相应结构之间的关系。为了在云母表面实验与固定电荷表面模拟之间建立定量联系，我们提出了一种确定离子液体中云母上有效表面电荷的实验程序。我们发现，最近通过力测量得出的结构交叉似乎受到了模拟的支持：在交叉处，电荷振荡结构切换为单调电荷，并且溶剂分层成为主导。最后，我们在组成表面电荷空间中画出了一个相图，描绘了电荷振荡界面结构的区域和电荷单调衰减的区域。我们注意到，结构和振荡力的这些特征不同于（与同时作用的）最近报道的由高浓度电解质中异常长的本体筛选长度引起的更长范围的单调力。