论文标题
电解质溶液的表面分层
The Surface of Electrolyte Solutions is Stratified
论文作者
论文摘要
离子在空气/水界面上的分布在许多自然过程中起着决定性的作用。通常可以理解，低电荷密度的可极化离子表面活性，这意味着它们位于水面顶部。在这里，我们通过将表面特异性杂项检测到的振动总和频率与神经网络辅助的AB始于从头算分子动力学模拟相结合，来修改这一已建立的假设。我们的结果直接表明，典型电解质溶液中的离子实际上位于地下区域，导致此类界面分层为两个独特的水层。最外面的表面被离子耗尽，地下层富含离子。结果，除了最外面的空气/水接口外，还出现了有效的液体/液体界面，在溶液内部埋葬了几个Å，形成了第二个水/电解质界面。
The distribution of ions at the air/water interface plays a decisive role in many natural processes. It is generally understood that polarizable ions with low charge density are surface-active, implying they sit on top of the water surface. Here, we revise this established hypothesis by combining surface-specific heterodyne-detected vibrational sum-frequency generation with neural network-assisted ab initio molecular dynamics simulations. Our results directly demonstrate that ions in typical electrolyte solutions are, in fact, located in a subsurface region leading to a stratification of such interfaces into two distinctive water layers. The outermost surface is ion-depleted, and the sub-surface layer is ion-enriched. As a result, an effective liquid/liquid interface buried a few Å inside the solution emerges, creating a second water/electrolyte interface, in addition to the outermost air/water interface.
