Coadsorption of CO and NO on the Pd(111) surface:: Combined ab initio and Monte Carlo study

Adsorption and coadsorption of nitric oxide (NO) and carbon monoxide (CO) on the Pd(111) surface are studied by combining first principles (FP) calculations and Monte Carlo (MC) simulations. From FP adsorption energies and molecule-molecule interactions we construct an interaction model, which is used in MC. We do several simulations with different coverages and CO/NO ratios. The simulations provide 0.75 monolayer (ML) for a saturation coverage, which is in excellent agreement with experiments. The results indicate that at 0.75 ML coverage, NO molecules take over the hollow sites and push CO molecules mainly onto bridge sites.