PERIODIC FORCING ON THE OSCILLATORY BEHAVIOR OF A REACTION SIMULATED BY MONTE CARLO
Mª Carmen Lemos, F. E. Gálvez, Antonio Córdoba
In this paper we study the reaction $N_{2}O + H_{2}$ catalyzed on a Ir (110) surface by Monte Carlo simulation (MC), focusing our study on the temporal evolution of the system. The phase diagram of the model, which represents the surface density of adsorbed species as a function of a control parameter, shows three distinct regions: an oscillatory region, which exhibits oscillations P1 (period-1, one maximum), between two stable steady regions. Results obtained are in good agreement with experiments conducted in the reaction. At a later stage and to analyze the stability of the observed P1 oscillations, we apply harmonic disturbances on the MC model. To do this we perturbed the P1 autonomous oscillations by periodic modulation of the partial pressure of one of the reactants. From the perturbed MC model interesting conclusions are drawn: when the external frequency is a half-integer of the natural frequency the behavior becomes aperiodic and quasiperiodic. In view of these results, we can affirm the existence of the Ruelle-Takens-Newhouse route to chaos in the perturbed MC model since it is observed that the chaotic state is obtained by breaking the quasiperiodic state.