Effect of dispersion correction on the Au(1 1 1)-H2O interface: A first-principles study

Abstract

A theoretical study of the H(2)O-Au(1 1 1) interface based on first principles density functional theory (DFT) calculations with and without inclusion of dispersion correction is reported. Three different computational approaches are considered. First, the standard generalized gradient approximation (GGA) functional PBE is employed. Second, an additional energy term is further included that adds a semi-empirically derived dispersion correction (PBE-D2), and, finally, a recently proposed functional that includes van der Waals (vdW) interactions directly in its functional form (optB86b-vdW) was used to represent the state-of-the art of DFT functionals. The monomeric water adsorption was first considered in order to explore the dependency of geometry on the details of the model slab used to represent it (size, thickness, coverage). When the dispersion corrections are included the Au-H(2)O interaction is stronger, as manifested by the smaller d(Au-O) and stronger adsorption energies. Additionally, the interfacial region between Au(1 1 1) slab surfaces and a liquid water layer was investigated with Born-Oppenheimer molecular dynamics (BOMD) using the same functionals. Two or three interfacial orientations can be determined, depending on the theoretical methodology applied. Closest to the surface, H(2)O is adsorbed O-down, whereas further away it is oriented with one OH bond pointing to the surface and the molecular plane parallel to the normal direction. For the optB86b-vdW functional a third orientation is found where one H atom points into the bulk water layer and the second OH bond is oriented parallel to the metal surface. As for the water density in the first adsorption layer we find a very small increase of roughly 8%. From the analysis of vibrational spectra a weakening of the H-bond network is observed upon the inclusion of the Au(1 1 1) slab, however, no disruption of H-bonds is observed. While the PBE and PBE-D2 spectra are very similar, the optB86b-vdW spectrum shows that the H-bonds are even more weakened.

Interaction of H2O and H2S with Cu(111) and the impact of the electric field: the rotating & translating adsorbate, and the rippled surface

“…This confirms that the lateral size corresponding to the effective surface coverage of 1/4 ML is too small to introduce a significant artificial interaction with its periodic images. The differences between the 4 × 2 √ 3 and 5 × 3 √ 3 supercells show that the adsorption geometry is more sensitive to the lateral size change than E ads , which agrees with the previous DFT studies on 4d metal surfaces 36,37 . Additionally, the greater α and smaller d Cu−O pattern for a larger surface supercell shows that the O atom gets closer to the surface with an increased surface size while H atoms remain relatively fixed in height.…”

Using molecular dynamics to quantify the electrical double layer and examine the potential for its direct observation in the in-situ TEM

“…We assume that these parameters are qualitatively sufficient for representing both the {111} and {100} facets of gold (see a comparative study that shows this to be reasonable for copper [30]; unfortunately, studies that consider both facets within the same work are rare which limits our ability to verify this assumption for gold [31]). The use of this simple model in simulation of the water-Au {111} interface gives generally good agreement with oxygen atom density profiles recently determined through dispersion-corrected ab initio molecular dynamics [32]. There is one exception to this agreement, however, as the ab initio simulations predict that the primary water layer at the gold surface is characterized by two density profile peaks as opposed to a single peak.…”

Modeling and simulation of protein–surface interactions: achievements and challenges

“…The computational overhead in using these functionals is modest, and they have also been applied to other biomolecules adsorbed on gold, such as nucleic acids (Rosa et al 2012(Rosa et al , 2014a. AIMD is also possible with these functionals, as exemplified by a recent study of the liquid water/gold interface (Nadler & Sanz, 2012). In this case, dispersion interactions do not change the picture provided by conventional functionals (Cicero et al 2011).…”

“…The umbrella sampling technique has been successfully employed for the calculation of the free energy of adsorption of a model surfactant on hydrophobic and hydrophilic silica surfaces (Xu et al 2008), nanoparticles on phospholipid membranes (Li & Gu, 2010), ions on hydrophobic surfaces (Horinek et al 2008) and amino acids on a ZnO surface (Nawrocki & Cieplak, 2013). Umbrella sampling combined with WHAM has also been applied to peptide-surface interactions.…”