Electron transport in a Pt-CO-Pt nanocontact: Density functional theory calculations

We have performed first-principles calculations for the mechanic and electric properties of pure Pt nanocontacts and a Pt contact with a single CO molecule adsorbed. For the pure Pt contacts we see a clear difference between point contacts and short chains in good agreement with experiments. We identify a tilted bridge configuration for the Pt-CO-Pt contact, which is stable and has a conductance close to 0.5G(0) (G(0)=2 e(2)/h), and we propose that this structure is responsible for an observed peak at 0.5G(0) in the conductance histogram for Pt exposed to a CO gas. We explain the main features of the transmission function for the Pt-CO-Pt contact, and show that the conductance is largely determined by the local d band at the Pt apex atoms.