Electron transport in a Pt-CO-Pt nanocontact: First-principles   calculations
  We have performed first-principles calculations for the mechanic and electric properties of pure Pt nano-contacts 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 $0.5G_0$ ($G_0=2e^2/h$), 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. 
M. Strange, K. S. Thygesen, K. W. Jacobsen