Surface-Charge Dependent Orientation of Water at the Interface of a Gold Electrode: A Cluster Study
Résumé
A gold/water interface has been investigated with the DFT-based self-consistent-charge density-functional tight-binding (SCC-DFTB) method using a cluster model. Born–Oppenheimer molecular-dynamics simulations for mono-, bi-, and trilayers of water on the surface of a Au55 cluster have been computed. We have demonstrated the applicability of this method to the study of the structural and dynamical properties of the gold/water-multilayer interface. The results of the simulations clearly show the charge-dependent orientation and the corresponding polarization of the water sphere around the gold cluster. However, it was also shown that this polarization is restricted almost only to the first solvation shell. This illustrates the rather short-range screening behavior of water. The present study builds the basis for further investigations of metal/electrolyte interfaces on a reliable atomistic level, avoiding the problems of spurious artifacts in models using periodic boundary conditions.