Alumina(0001)/Water Interface: Structural Properties and Infrared Spectra from First-Principles Molecular Dynamics Simulations

We investigated the atomic structure and infrared spectra of the alumina(0001)/water interface, using first-principles molecular dynamics simulations based on density functional theory within the generalized gradient approximation. The computed structural properties of the interface are in good agreement with the results of synchrotron X-ray experiments. Detailed analyses of the computed infrared spectra revealed two types of water molecules at the hydrophilic oxide/water interface: molecules participating in strong ice-like hydrogen bonding with the oxide surface and molecules involved in weaker liquid-like hydrogen bonding. Our results provide a molecular interpretation of the ice-like and liquid-like bands observed in sum-frequency vibrational spectroscopy experiments and underscore the significance of strong hydrogen-bonding interactions in determining the orientation of interfacial water molecules.