Conductance of a hydrogen molecule

Recently Smit et al. [Nature 419, 906 (2002)] have reported that a single hydrogen molecule can form a bridge between Pt electrodes, which has a conductance close to one quantum unit, carried by a single channel. We present density functional calculations explaining these experimental findings. We show that the symmetry of the molecular orbitals selects a single conduction channel. The transmission of this channel is close to unity due to a combination of the charge transfer between hydrogen and the Pt contacts and the strong hybridization between the bonding state of the molecule and the d-band of the Pt leads.