Simulation of the XANES spectrum of the ideal PB structure, with K + on the 8c site, is compared in Figure with the experimental spectra of HC-PB. The pre-edge (Feature A), white line shoulder (Features B & C) and white line (Feature D) were successfully simulated. These features are attributed from the projected DOS (Figures and) to low lying K p-states overlapped with Fe orbitals (A), hybridized K pstates with CN anti-bonding π orbitals (B & C), and isolated K p-states (D), respectively. While most features are well represented, the intensity of feature C is significantly underestimated in the original simulation. Given that K + at the 8c site is a significant distance from CN π anti-bonding orbitals, a lack of overlap between K p-states and these π orbitals can account for the low intensity of feature C and dominance of D. As noted, when performing the DFT simulations, the inclusion of water molecules or defects pushes K + towards the Fe 3+ -N corners of the primitive cube (32f' position), which would increase orbital overlap of states associated with feature C. XANES simulation of K + within this 32f' position (Figure ) did indeed show an increased contribution to the XANES from feature C and brought the XANES simulation into closer agreement with experiment. The greater ΔH form calculated by DFT suggests that that K + does not reside within the defect (Fig. ); with the evidence is more compelling for K + being forced into the corners of the channels by these defect sites or occluded water within the structure.