Chemical turbulence and standing waves in a surface reaction model: The influence of global coupling and wave instabilities

Abstract

Among heterogeneously catalyzed chemical reactions, the CO oxidation on the Pt(110) surface under vacuum conditions offers probably the greatest wealth of spontaneous formation of spatial patterns. Spirals, fronts, and solitary pulses were detected at low surface temperatures (T<500 K), in line with the standard phenomenology of bistable, excitable, and oscillatory reaction-diffusion systems. At high temperatures (T greater, similar 540 K), more surprising features like chemical turbulence and standing waves appeared in the experiments. Herein, we study a realistic reaction-diffusion model of this system, with respect to the latter phenomena. In particular, we deal both with the influence of global coupling through the gas phase on the oscillatory reaction and the possibility of wave instabilities under excitable conditions. Gas-phase coupling is shown to either synchronize the oscillations or to yield turbulence and standing structures. The latter findings are closely related to clustering in networks of coupled oscillators and indicate a dominance of the global gas-phase coupling over local coupling via surface diffusion. In the excitable regime wave instabilities in one and two dimensions have been discovered. In one dimension, pulses become unstable due to a vanishing of the refractory zone. In two dimensions, turbulence can also emerge due to spiral breakup, which results from a violation of the dispersion relation.

Nonlinear physics of electrical wave propagation in the heart: a review

“…As a result, the defect number fluctuates in time according to a Poisson distribution and the variance of the defect number was predicted to be equal to its temporal mean [341]. Studies of the defect-statistics in the Bär-Eiswirth model [342,343] revealed that spiral breakup leads to an initial fast transient increase of the defect number, but shows substantial deviations from the prediction of the model by Gil et al In particular, the variance close to the breakup instability is much smaller than the mean, which is due to a strong anticorrelation between topological defects reminiscent of the spatial correlation of particles in a liquid. Further away from the breakup instability spatial correlations are much weaker and the defect statistics are in line with the prediction of the simple theory by Gil et al [341].…”

CO-activator model for reconstructing Pt(100) surfaces: Local microstructures and chemical turbulence

“…It should be noted that the inhomogeneous oscillating states and standing waves have been previously discussed for CO oxidation on Pt(110) where the main mechanism responsible for these phenomena is the coupling through the gas phase [10,11,12]. In contrast to Pt(110), on Pt(100) the inhomogeneities in the surface geometry play a central role.…”

New type of the source of travelling impulses in two-variable model of reaction–diffusion system

“…Also the 1D version of the model suggested for describing a surface reaction (CO oxidation on Pt(110)) [39] is promising, because the qualitative change of the pattern with the size of the system might be observed experimentally, provided that the experimental setup was as close to 1D as possible. It is worth noting that our model is also realistic and could be realized in experiments in a 1D CFUR with two enzymatic reactions.…”