Modelling of phase transitions and reaction at CO adsorption on oxygen precovered Pd(1 1 1)

Using the interaction parameters up to the third neighbors and activated form of O and CO diffusion and their reaction, the model has been proposed for Monte-Carlo simulations describing the catalytic O + CO → CO ₂ reaction and occurring phase transitions on Pd(1 1 1) surface. Upon adsorption of CO the pre-adsorbed oxygen transforms from p(2 × 2) _O phase into sqrt(3) × sqrt(3) R 30 _O ° and sqrt(3) × sqrt(3) R 30 _O ° → p (2 × 1) _O phases in the limit of room and moderate temperatures, respectively. We demonstrate that the kinetic effects determine both the occurrence of the p(2 × 1) _O and disappearance of the sqrt(3) × sqrt(3) R 30 _O ° phases at moderate and low temperatures, respectively. Using reaction rate as a fit parameter, we show that at room temperature the start of the reaction can be synchronized with the occurrence of sqrt(3) × sqrt(3) R 30 _O ° phase.