Dependence of Water Dynamics on Molecular Adsorbates near Hydrophobic Surfaces: First-Principles Molecular Dynamics Study

First-principles molecular dynamics simulations are used to gain an atomistic-level insight into how the molecular behavior of interfacial water is influenced by specific surface adsorbates. Although the overall hydrophobic versus hydrophilic character of a given surface is widely recognized to be important in determining the behavior of interfacial water molecules, we show that subtle molecular details may also play a role in determining the dynamical behavior of water. By comparing water diffusivity at three different nonpolar surfaces, we find that specific surface features can lead to a suppression of hydrogen bond network ring structures by enhancing hexagonal spatial distributions of water molecules near the surface. Such a distinct molecule-dependent behavior of the interfacial water was found to persist well into the liquid, while most structural properties are noticeably influenced in only the first water layer.