These deviations can be interpreted as delocalization of the charges on the transition metals, especially nickel, as the calculated UPE of ca. 1.7 is lower than the theoretical value of 2 for Ni 2+ . This delocalization is also visible in the spin density difference (SDD) plots of the discharged materials in Figure , as mainly oxygen anions bonded to nickel ions show some additional spin-up density. When charged to 4.4 V, the fluctuations in UPE values on oxygen must be assigned not only to delocalization of the transition metal oxidation but also to direct oxidation of the oxygen ions, which agrees with the experimental RIXS measurements (Figure ). In particular, one oxygen ion (out of 72) in the Mg-doped material shows a very strong oxidation with a UPE of more than 0.5. This strong oxidation can be assigned to an oxidation of O 2-to O 1-that would have a theoretical charge of UPE from 0 to 1 (2s 2 2p 6 → 2s 2 2p 5 ). It should be noted that this oxygen ion is directly bound to a Mg 2+ ion which supports the experimental hypothesis that oxygens close to Mg ions are oxidized more strongly. It can be assumed that a driving force for the oxidation of oxygen close to Mg is the electrostatic interaction, as it shows the smallest decrease of attractive forces for decreasing the negative charge of an oxygen from 2-to 1-next to the cation with the smallest positive charge (Mg 2+ ). Even though the most oxidized single oxygen ion is found in the O3-NaMNMO material, the sum of absolute UPE on all oxygens in the which is also in good agreement with the trends observed in the experimental study.