Surface phase transitions at O and CO catalytic reaction on Pd(1 1 1)

The model has been proposed to simulate numerically the reaction O + CO → CO2 and occurring phase transitions on Pd(1 1 1) surface. We calculate the phase diagram for this system by kinetic Monte Carlo method. It shows the phase transitions p(2×2)O→3×3R30O° and p(2×2)O→3×3R30O°→p(2×1)O with increase of CO coverage for room and intermediate temperatures, respectively, while in the low temperature limit the direct p(2 × 2)O → p(2 × 1)O phase transition is observed. We demonstrate that the reaction rate is the crucial factor determining the occurrence of the p(2 × 1)O phase and vanishing of the 3×3R30O° with decrease of temperature. The results indicate that the reaction proceeds inside both the p(2 × 2)O and 3×3R30O° phases, but on the perimeter of the domains of p(2 × 1)O structure.