Desorption kinetics from structurally disordered and energetically heterogeneous surfaces: noninteracting and weakly interacting adsorbates

We present a computational study on the kinetics of desorption from a structurally disordered and energetically heterogeneous surface. The structural disorder is in the form of varying numbers of nearest neighbors per site (from zero to six). To add energetic heterogeneity, each site has an effective binding energy that is the sum of the binding energy of the overall surface plus a nearest neighbor contribution, which is calculated as the product of the coordination number z times a percentage of the surface binding energy. We find that, in the absence of lateral interactions, the thermal desorption spectrum can be fit with the Polanyi-Wigner equation for a wide range of nearest neighbor energetic contributions. After some percentage maximum, the overall desorption peak exhibits some features that characterize surfaces where the differences in energies for different binding sites are large enough to cause the overall peak to `split' and appear as an overlap of multiple peaks. Since we observe a very close fit to the analytical result for nearest neighbor contributions below this maximum, we explore wether exact surface parameters (mainly the energy of activation E_a) can be extracted from the corresponding Arrhenius plots, or part of them, and we investigate if there is any consistency that could help to obtain accurate information for disordered surfaces that have similar characteristics. We also explore if this can be applied in the presence of lateral interactions within the physisorption range.