To assess the completeness of the search and prevalence of alternative low energy O 2 dimer arrangements, we perform a second structure search in which the (displaced) nickel positions are varied. Here we take the lowestenergy stable O-O dimer structure, which contains a single nickel atom that has displaced into the vacant layer, and remove this migrated nickel. The nickel atom is then reinserted at each possible interstitial site identified via Voronoi tessellation of the structure in turn, yielding a second generation of dimer-trial structures which are then relaxed. No new low-energy structures are discovered from this process; however, many are found to be lower energy relative to other unstable dimer structures found in the initial search. The energies of the "reinserted Ni" calculations are highlighted in fig. . These results highlight several important points. First, given the endothermic formation energy of the O 2 dimer configurations, it is unlikely that small reconstructions to accommodate the formation of an oxygen dimer will be more stable than the "pristine" layered system. This indicates good kinetic stability of layered NiO 2 towards the formation of oxygen dimers, despite its thermodynamic preference to decompose into NiO and O 2 . Second, vacant sites in the nickel layer are likely to enable oxygen dimer formation.