Electronic transport and vibrational modes in a small molecular bridge: H-2 in Pt nanocontacts

We present a state-of-the-art first-principles analysis of electronic transport in a Pt nanocontact in the presence of H-2 which has been recently reported by Smit [Nature (London) 419, 906 (2002)]. Our results indicate that at the last stages of the breaking of the Pt nanocontact two basic forms of bridge involving H can appear. Our claim is, in contrast to the claim of Smit , that the main conductance histogram peak at Gapproximate to2e(2)/h is not due to molecular H-2, but to a complex Pt2H2 where the H-2 molecule dissociates. A first-principles vibrational analysis that compares favorably with the experimental one also supports our claim.