A statistical rate theory description of CO diffusion on a stepped Pt(111)surface

The statistical rate theory approach is used to describe far-from-equilibri um diffusion of carbon monoxide on a stepped Pt(111) surface at low total c overages. Under nonequilibrium conditions, migration of adsorbates from ter races to steps, where adsorbates are more strongly bound, can occur. An exp ression for the molecular transport rate between terraces and steps is deri ved in terms of an equilibrium exchange rate, and the instantaneous chemica l potentials of the molecules adsorbed on the terraces and along the steps. The theory contains no free parameters. Both the equilibrium exchange rate and the chemical potentials are obtained in the framework of a lattice gas model. The time evolution of the populations of steps and terraces is calc ulated and used to fit the available experimental data in order to evaluate the activation barrier of diffusion on terraces and the associated prefact or. (C) 1999 American Institute of Physics. [S0021-9606(99)71727-7].