Surface diffusion on energetically heterogeneous surfaces-an effective medium approximation approach

A model based on the effective medium approximation is presented which describes surface diffusivity on an energetically heterogeneous surface as a function of overall surface coverage and a heterogeneity parameter. The heterogeneity parameter is obtained independently from the equilibrium adsorption data. The effect of heterogeneity on surface diffusion depends on the relationship between the activation energy of surface diffusion and the energy of adsorption. The effect of the coordination number is discussed. On comparison with other models for both heterogeneous and homogeneous surfaces, it is shown that the model proposed in this work gives a better representation of the experimental data.