Water orientation and hydrogen-bond structure at the fluorite/water interface.
Water orientation and hydrogen-bond structure at the fluorite/water interface.
复制标题
DOI：
10.1038/srep24287
复制
发表时间：
2016-04-12
影响因子：
4.6
通讯作者：
Sulpizi M
中科院分区：
文献类型：
--
作者：
Khatib R;Backus EH;Bonn M;Perez-Haro MJ;Gaigeot MP;Sulpizi M
与矿物界面接触的水对各种不同的过程都很重要。在这里，我们提出了一项结合理论/实验的研究，该研究提供了对普遍存在且重要的CaF2/水界面的定量，分子水平的理解。我们的研究结果表明，在低pH下，表面带正电，导致相当程度的水有序。表面电荷主要来自氟离子的溶解，而不是质子在表面的吸附。在高pH下，我们观察到Ca-OH指向水中的存在。这些OH基团与周围水的相互作用非常弱，并负责VSFG光谱中的“自由OH”特征，这可以从局部电子结构效应来解释。通过结合CaF2/水界面的高级相位分辨振动和频率生成谱和最先进的从头算分子动力学模拟（包括电子结构效应），可以定量地分析表面终止、近表面离子分布和水的排列。
Water in contact with mineral interfaces is important for a variety of different processes. Here, we present a combined theoretical/experimental study which provides a quantitative, molecular-level understanding of the ubiquitous and important CaF2/water interface. Our results show that, at low pH, the surface is positively charged, causing a substantial degree of water ordering. The surface charge originates primarily from the dissolution of fluoride ions, rather than from adsorption of protons to the surface. At high pH we observe the presence of Ca-OH species pointing into the water. These OH groups interact remarkably weakly with the surrounding water, and are responsible for the “free OH” signature in the VSFG spectrum, which can be explained from local electronic structure effects. The quantification of the surface termination, near-surface ion distribution and water arrangement is enabled by a combination of advanced phase-resolved Vibrational Sum Frequency Generation spectra of CaF2/water interfaces and state-of-the-art ab initio molecular dynamics simulations which include electronic structure effects.