In addition to identifying the two main XAS peaks, the prepeak at 1563 eV was also reproduced. A pre-edge is documented for 𝛼-Al2O3, at 1565 eV, which occurs because of transitions from the 1s to 3s states in Al . While this transition is normally dipole forbidden, the presence of atomic vibrations results in distorted octahedral environments and bond lengthening which causes p-s mixing to occur and allow this transition. The pre-edge in a-Al2O3 is at 1562 to 1563 eV, both in experiment and in the calculated spectra, as shown in Fig. , and occurs in either tetrahedral Al(IV) sites or square pyramidal Al(V) sites. Similarly to the 𝛼-Al2O3 case, this pre edge is a result of site distortions at the Al(IV) site (Fig. ) . The calculated XAS spectra suggests a possible origin of this pre-edge feature, arising from Al(IV) sites as well as the absorption energy of the Al(V) peaks, which are masked in experiment, as their absorption energies overlap with transitions in Al(IV) environments.