This simulation is of an atomic-level Kinetic Monte Carlo (KMC) simulation of CO oxidation of the (111) surface of platinum. You first see disordered adsorption of CO on the surface. Over time, the CO configuration evolves into a regular pattern. Finally, the CO on the surface combines with oxygen to form CO2 molecules, which desorb from the surface. These KMC simulations require binding energies, reaction barriers, and rate constants for all the species and processes that occur on the surface. We obtain these data by quantum mechanical calculations.