@article{MelaniNagataWirthetal.2018,
  author    = {Melani, Giacomo and Nagata, Yuki and Wirth, Jonas and Saalfrank, Peter},
  title     = {Vibrational spectroscopy of hydroxylated alpha-Al2O3(0001) surfaces with and without water},
  series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  volume    = {149},
  journal   = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  number    = {1},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0021-9606},
  doi       = {10.1063/1.5023347},
  pages     = {10},
  year      = {2018},
  abstract  = {Using gradient- and dispersion-corrected density functional theory in connection with ab initio molecular dynamics and efficient, parametrized Velocity-Velocity Autocorrelation Function (VVAF) methodology, we study the vibrational spectra (Vibrational Sum Frequency, VSF, and infrared, IR) of hydroxylated alpha-Al2O3(0001) surfaces with and without additional water. Specifically, by considering a naked hydroxylated surface and the same surface with a particularly stable, "ice-like" hexagonal water later allows us to identify and disentangle main spectroscopic bands of OH bonds, their orientation and dynamics, and the role of water adsorption. In particular, we assign spectroscopic signals around 3700 cm(-1) as being dominated by perpendicularly oriented non-hydrogen bonded aluminol groups, with and without additional water. Furthermore, the thin water layer gives spectroscopic signals which are already comparable to previous theoretical and experimental findings for the solid/(bulk) liquid interface, showing that water molecules closest to the surface play a decisive role in the vibrational response of these systems. From a methodological point of view, the effects of temperature, anharmonicity, hydrogen-bonding, and structural dynamics are taken into account and analyzed, allowing us to compare the calculated IR and VSF spectra with the ones based on normal mode analysis and vibrational density of states. The VVAF approach employed in this work appears to be a computationally accurate yet feasible method to address the vibrational fingerprints and dynamical properties of water/metal oxide interfaces. Published by AIP Publishing.},
  language  = {en}
}
@article{HeidenWirthCampenetal.2018,
  author    = {Heiden, Sophia and Wirth, Jonas and Campen, Richard Kramer and Saalfrank, Peter},
  title     = {Water molecular beam scattering at alpha-Al2O3(0001)},
  series = {The journal of physical chemistry : C, Nanomaterials and interfaces},
  volume    = {122},
  journal   = {The journal of physical chemistry : C, Nanomaterials and interfaces},
  number    = {27},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1932-7447},
  doi       = {10.1021/acs.jpcc.8b04179},
  pages     = {15494 -- 15504},
  year      = {2018},
  abstract  = {Recent molecular beam experiments have shown that water may adsorb molecularly or dissociatively on an α-Al2O3(0001) surface, with enhanced dissociation probability compared to "pinhole dosing", i.e., adsorption under thermal equilibrium conditions. However, precise information on the ongoing reactions and their relative probabilities is missing. In order to shed light on molecular beam scattering for this system, we perform ab initio molecular dynamics calculations to simulate water colliding with α-Al2O3(0001). We find that single water molecules hitting a cold, clean surface from the gas phase are either reflected, molecularly adsorbed, or dissociated (so-called 1-2 dissociation only). A certain minimum translational energy (above 0.1 eV) seems to be required to enforce dissociation, which may explain the higher dissociation probability in molecular beam experiments. When the surface is heated and/or when refined surface and beam models are applied (preadsorption with water or water fragments, clustering and internal preexcitation in the beam), additional channels open, among them physisorption, water clustering on the surface, and so-called 1-4 and 1-4′ dissociation.},
  language  = {en}
}