While this calls for substantial methodological advances to boost the microkinetic model- ing capabilities, we can already gain first qualitative insight by analyzing selected sequences of the identified elementary processes. Figure shows a corresponding six-step pathway for the system containing only two O atoms per surface unit-cell and thus characteristic for the very initial oxidation of the step edge. Starting from the smooth (110)-type step of the (410) vicinal, a first lowest-barrier process (0.33 eV) starts to pull out one Pd step atom. This is a typical example of facile O-induced restructuring as the cost of the lower coordination of the Pd atom is mitigated by one of the attached O atoms moving from its original three-fold coordinated upper step edge site to an equally three-fold coordinated anchor site further away from the step. The second still low-barrier process (0.63 eV) continues this pulling out with the peripheral O atom moving to an equivalent site even further out. Of special note is the fact that this resulting state (number 3 in Fig. ) is 0.16 eV more stable than the starting state. In contrast, the analogous rupturing of a Pd atom out of the (100) step without coordinating O atoms is uphill by 0.32 eV and involves a barrier of 0.84 eV. There is no O-free intermediate that corresponds with state 2 (cf. Fig. ). Without O, this structure is not stabilized enough to persist. From system state 3, cf. The next three processes of the pathway equally allow to make contact with previous reports, namely step bunching on vicinal Pd surfaces as observed experimentally under oxidizing conditions by scanning tunneling microscopy and under conditions of CO oxidation by surface X-ray diffraction. Two of these three processes have somewhat higher barriers up to 1.43 eV, but by involving multiple atoms in a collective row-shift motion they efficiently allow to transport Pd atoms from one edge to another, inducing the growth of the terrace with O-decorated step edge at the expense of a retracting neighboring terrace (cf.