Through it, the system could thus in principle dynamically interconvert between the involved system states. Given the low barriers of the processes connecting in particular system states 1 through 4, this interconversion between the corresponding smooth and zig-zag step edge structures would be quite fast (see Fig. for the corresponding rates). Such a dynamic O-induced step restructuring would be consistent with a fuzzy resolution of near-step regions in scanning tunneling and transmission electron microscopy at experimental scan rates. Moreover, the barriers are in fact so low that this pathway suggests a potential fluxional behavior of the active surface. The reactivity of the ( ) and (111) type edges is quite different and if these edge types interconvert readily during the catalytic cycle, this operando evolution could be crucial to understand the catalytic performance of the working surface. Very similar conclusions are obtained from another restructuring pathway, now at higher O loading of six O atoms per surface unit-cell. As summarized in Fig. , two processes with barriers below 0.4 eV bring the system efficiently from a step-decorated state into an energetically much lower superbasin. Within this superbasin, most processes are below 0.9 eV, with barriers exiting state 5 at 1.2 eV. These low-energy processes bring the system readily between system states 3 through 6, e.g. at 600 K at rates faster than ∼ 10 3 s -1 (Fig. ). At time scales of the oxidative catalysis, the system could thus dynamically evolve over the corresponding quite different edge structures with their correspondingly different reactivities. States 3 and 4 exhibit e.g. large Pd x O y chains forming a ring that roughens the step edge and pushes it forward, leaving vacancies in the terrace behind the edge. In contrast, state 6 involves fins of Pd 3 O 4 extending from the step edge, without any vacancies within the Pd x O y structures. Time averaged, there is thus a mix of two-and three-fold O coordination in the restructured step edges. This would match with experimental X-ray photoelectron spectroscopy data, while the fast interconversion would again be consistent with the fuzzy images of step edges in scanning microscopies. Notwithstanding, we repeat that only a comprehensive microkinetic analysis could assess the true relevance of this pathway under reaction conditions, and neither can we be sure that the present APE search starting from the step-decorated structures identified all relevant elementary processes. Nevertheless, the framework does provide a more systematic access to the underlying elementary processes and it is baffling that only three non-intuitive and thus hitherto not considered collective processes provide an efficient pathway to interconvert between such radically different step edge structures.