Transport in molecular junctions with different metallic contacts

Ab initio calculations of phenyl dithiol connected to Au, Ag, Pd, and Pt electrodes are performed using nonequilibrium Green's functions and density functional theory. For each metal, the properties of the molecular junction are considered both in equilibrium and under bias. In particular, we consider in detail charge transfer, changes in the electrostatic potential, and their subsequent effects on the I-V curves through the junctions. Gold is typically used in molecular junctions because it forms strong chemical bonds with sulfur. We find, however, that Pt and Pd make better electrical contacts than Au. The zero-bias conductance is found to be greatest for Pt, followed by Pd, Au, and then Ag.