Abstract
Adsorption of pyridine on Rh, Pd, Pt, and Ni(1 1 1) is investigated using density functional theory with five van der Waals inclusive functionals (optB86-vdW, optB88-vdW, optPBE-vdW, revPBE-vdW, and the rPW86-vdW2), and PBE. The two most energetically favorable configurations were either a vertical configuration with the molecule's N atom bonded to a metal atom or a flat configuration with center of the molecule's ring over a bridge site with the N atom close to a metal atom. We find that whether the equilibrium adsorption configuration is a flat or vertical depends strongly on the choice of functional and metal. This sharp contrast in final adsorption configurations demonstrates the difficulty current methods have in calculating the adsorption of pyridine on transition metal surfaces, especially Ni(1 1 1). Along with the final adsorption configurations, we present various geometric and electronic properties of the equilibrium adsorption configurations including adsorption heights, buckling of the first layer of the substrate, tilt angle of the molecule, charge transfer to/from the molecule, change in the surface's work function, and change in the surface's d-band upon the adsorption of pyridine.