Kinetic model for surface reconstruction.

A microscopic kinetic model for the alpha <==> beta [e.g., hex <==> 1x1 for Pt(100) and 1x2 <==> 1x1 for Pt(110)] surface reconstruction is investigated by means of the mean field approximation and Monte Carlo simulations. It considers homogeneous phase nucleation that induces small surface phase defects. These defects can grow or decline via phase border propagation in dependence on the chemical coverage by an adsorbate A (CO). An asymmetry in the adsorbate surface diffusion from one surface phase to the other gives rise to two critical coverages that determine the intervals of stability of the homogeneous alpha phase, the dynamically stable heterogeneous state, and the homogeneous beta phase. Both surfaces show a very similar qualitative behavior regarding the phase transitions that are of second order in both cases. As a result the experimentally observed nonlinear island growth rate and the critical coverages can be explained at a quantitative level.