Contact dependence of the conductance of H2 molecular junctions from first principles

Using a first-principles scattering-state approach, transport properties of molecular hydrogen in Pd and Pt junctions are computed, revealing a dramatic reduction in conductance when replacing Pt with Pd contacts. This decrease originates from a change in conduction mechanism, from ballistic transport in Pt junctions to off-resonance tunneling in Pd junctions. Our findings also indicate that lead atoms in contact with H2 are as important in determining conductance as H2 itself.