Electron transport in aPt−CO−Ptnanocontact: 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 $\mathrm{Pt}\text{\ensuremath{-}}\mathrm{CO}\text{\ensuremath{-}}\mathrm{Pt}$ contact, which is stable and has a conductance close to $0.5{G}_{0}$ $({G}_{0}=2\phantom{\rule{0.3em}{0ex}}{e}^{2}∕h)$, and we propose that this structure is responsible for an observed peak at $0.5{G}_{0}$ in the conductance histogram for Pt exposed to a CO gas. We explain the main features of the transmission function for the $\mathrm{Pt}\text{\ensuremath{-}}\mathrm{CO}\text{\ensuremath{-}}\mathrm{Pt}$ contact, and show that the conductance is largely determined by the local $d$ band at the Pt apex atoms.