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

We present the results of the modeling of CO adsorption and catalytic CO oxidation on inhomogeneous Pt(100) surfaces which contain structurally different areas. These areas are formed during the CO-induced transition from a reconstructed phase with hexagonal geometry of the overlayer to a bulklike (1 x 1) phase with square atomic arrangement. In the present approach, the surface transition is explained in terms of nonequilibrium bistable behavior. The bistable region is characterized by a coexistence of the hexagonal and (1 x 1) phases and is terminated in a critical bifurcation point which is located at (T(c) approximately 680 K, p(CO)(c) approximately 10 Torr). Due to increasing fluctuations, the behavior at high temperatures and pressures in the vicinity of this cusp point should be qualitatively different from the hysteresis-type behavior which is typically observed in the experiments under ultrahigh vacuum conditions. On the inhomogeneous surface, we find a regime of nonuniform oscillations characterized by random standing waves of adsorbate concentrations. The resulting spatial deformations of wave fronts allow us to gain deeper insight into the nature of irregular oscillations on Pt(100) surface.