First-Principles Studies of Single-Molecule Junctions: Conductance and Mechanically-Controlled Switching*

We explore the conductance of amine- and pyridine-Au single-molecule junctions, in the context of recent experiments, with a density-functional theory (DFT)-based scattering state approach. Using a physically motivated self-energy correction, we compute conductance values in good agreement with experiment, in contrast to DFT values that are too large[1]. We investigate quantitatively conductance trends, and demonstrate, together with experiment, that reversible conductance switching can result from mechanically-induced changes in the metal-molecule contact geometry in pyridine-Au junctions. [1] Quek et al, Nano Lett 7, 3477 (2007)