Effect of surface morphology on kinetic compensation effect: interactions vs. energetic heterogeneity

The kinetic compensation effect, observed in many fields of science, is the systematic variation in the apparent magnitudes of the Arrhenius parameters, the activation energy E_a and the preexponential factor ν, as a response to perturbations. In principle, a change in E_a results in a change in the configurational entropy of the system, which appears as variations in ν throughout an activated process. As part of a systematic study, we compare the effects of interactions on these parameters during the thermal desorption of quasi spherical molecules from a 2D glassy surface to the effects of surface energetic heterogeneity. The results of this study show that the decrease in configurational entropy is more pronounced in the presence of interactions. We also explore the role that diffusion plays in the extent to which the parameters offset each other. These results provide a deeper insight into the microscopic events from which compensation effects and isokinetic relations originate in this system, suggesting similar mechanisms may be at play in other systems where compensation
effects have been reported, and which can improve our understanding of the mechanisms which control the rates of many activated processes.