We employ normal-incidence x-ray standing wave and temperature programmed desorption spectroscopy to derive the adsorption geometry and energetics of the prototypical molecular switch azobenzene at Ag(111). This allows to assess the accuracy of semi-empirical correction schemes as a computationally efficient means to overcome the deficiency of semi-local density-functional theory with respect to long-range van der Waals (vdW) interactions. The obtained agreement underscores the significant improvement provided by the account of vdW interactions, with remaining differences mainly attributed to the neglect of electronic screening at the metallic surface..
The original publication is available at Phys.Rev. Letters by link DOI: 10.1103/PhysRevLett.104.036102