Pattern Formation, Reconstruction, and Roughening on a Catalytic Surface

Abstract

Catalytic reactions on oriented single crystals often exhibit rate oscillations and produce a variety of spatio-temporal patterns on a micron scale. The most thoroughly studied system of this kind is CO oxidation on Pt(l 10). The mechanism of rate oscillations and pattern formation under isothermal conditions at low pressure is based on a adsorbate-induced surface phase transition controlled by the CO coverage. The pattern formation on a micron scale can be modeled with the help of phenomenological mean-field equations containing a fraction of surface covered by one of the surface phases as a control variable. Mean-field theory cannot, however, capture many essential features of surface reconstruction, which involves material transport in a nanoscale range and is inadvertently linked to surface roughening.

We have carried out kinetic Monte-Carlo simulations of surface phase transitions on Pt(110) surface coupled to kinetic oscillations. Detailed data on bonding and activation energies of Pt atoms in different neighborhood configurations are extracted (and partly fitted and reconciled) from available ab initio computations and STM data, and used for computation of surface phase transitions and roughening. A realistic picture of kinetic oscillations and waves can be obtained with the help of a simplified Monte-Carlo model coupled to a mean field reaction-diffusion model.