We repeat the dimer-searching approach within this model system with some modifications. To accommodate the twin boundary, we use a larger cell (240 atoms, 11.03 Å × 10.88 Å × 19.48 Å). The structure is shown in fig. . Due to the increased computational expense in calculating this structure, each trial structure is ini-tially relaxed with DFT+U . The same displaced nickel ion reinsertion procedure was performed in the lowest energy structure at every Voronoi interstitial site as before. The results of this search are shown in fig. . Finally, owing to the known over-binding of oxygen molecules within (semi)-local DFT, we take the five lowest energy structures and recalculate their energies using the coarse calculation settings used in the initial hybrid DFT search in R 3m NiO 2 and confirm that all five structures found are lower energy than the dimer-free twin boundary structure. These results are also shown in the bottom panel of fig. . This result shows the generality of the model that oxidized oxide ions can stabilize by forming oxygen dimers at defects in LiNiO 2 in high states of charge. Despite the HSE06 dimer calculations remaining more stable than the twin-boundary structure, the stabilization introduced by dimer formation is reduced relative to the analogous DFT+U calculations, highlighting issues with structural searches for oxygen dimerization in cathode materials using DFT+U with corrections applied only to the transition metal d states. The two dimer structures that are less than 0.5 eV more stable than the twin boundary have relaxed to form oxygen trimers between themselves and a framework oxygen, as opposed to dimers, which are ultimately less stable than the molecular oxygen like dimer species in the other calculations.