Figure 5.

(a) Energetics of the structural models of the P^′3 phase shown in Figure 4 as obtained from hybrid functional DFT calculations. The energy states are labeled with their respective Ni-O₆ coordination environments as highlighted in Figure 4c/f. (b) Predicted ²³Na Fermi contact shifts for the three structural models. Both the spin-disproportionated (SD) ground state and the Jahn–Teller distorted (DFT-JT) state with a similar energy are predicted to exhibit resonances at significantly smaller shifts than the experimental spectrum. The predicted resonance of the experimental SXRD/NPD corefined structure shows excellent agreement with the experimental spectrum.