  The adsorption of 1,4-benzenediamine (BDA) on the Au(111) surface and
azobenzene on the Ag(111) surface is investigated using density functional
theory (DFT) with a non-local density functional (vdW-DF) and a semi-local
Perdew-Burke-Ernzerhof (PBE) functional. For BDA on Au(111), the inclusion of
London dispersion interactions not only dramatically enhances the
molecule-substrate binding, resulting in adsorption energies consistent with
experimental results, but also significantly alters the BDA binding geometry.
For azobenzene on Ag(111), the vdW-DF produces superior adsorption energies
compared to those obtained with other dispersion corrected DFT approaches.
These results provide evidence for the applicability of the vdW-DF method and
serves as a practical benchmark for the investigation of molecules adsorbed on
noble metal surfaces.
