Electronic transport properties ofPd‐Hjunctions between twoPdHx(x=0,0.25,0.5,0.75,1)electrodes: A nonequilibrium Green’s function study

Abstract

Using a fully self-consistent nonequilibrium Green's function method combined with the density functional theory, the transport properties of $\mathrm{Pd}\ensuremath{-}\mathrm{H}$ junctions between two $\mathrm{Pd}{\mathrm{H}}_{x}$ $(x=0,0.25,0.5,0.75,1)$ electrodes are investigated systematically. Three different hydrogen bridges are considered, including a single hydrogen atom configuration, a hydrogen molecule configuration with the $\mathrm{H}\mathrm{H}$ bond axis parallel to the transport direction and a complex ${\mathrm{Pd}}_{2}{\mathrm{H}}_{2}$ configuration where the ${\mathrm{H}}_{2}$ molecule dissociates. For the pure Pd nanojunction, the transmission spectrum drops sharply near the Fermi level and gives an average conductance of about $1.8{G}_{0}$. Four channels are found to have significant contributions to the conductance. The electronic structures of the electrodes are modified by the doping of H in the bulk. The presence of hydrogen between and in two electrodes changes the transmission spectra obviously, while the number of the eigenchannels of the junction is only determined by the electronic structure of the neck region. For the pure Pd electrodes, the calculated conductances of three kinds of hydrogen bridges are about 1.1, 0.5, and $0.9\phantom{\rule{0.3em}{0ex}}{G}_{0}$, respectively. For the heavy doping of H in the Pd electrodes, the conductances of hydrogen bridges with a hydrogen molecule or complex ${\mathrm{Pd}}_{2}{\mathrm{H}}_{2}$ configurations range from 0.3 to $0.7\phantom{\rule{0.3em}{0ex}}{G}_{0}$. The calculated results agree very well with the experimental values.