The observation that all materials in this study with low mean alignment-weighted frequencies also exhibited low migration barriers suggests that our metric could be used in combination with others to filter out materials with high barriers in screening studies. Other metrics that have been considered previously, including lattice geometry or polarizability, could prove useful in this regard. Polarizability may be particularly important for multivalent ion conductors due to the 2 + charge of the migrating cation. Alternatively, a prior study has demonstrated the importance of anharmonic effects, which were neglected in this study, for accurately predicting ion diffusion rates. 106 Although a full treatment of all anharmonic effects is likely too computationally expensive for the large-scale screening applications mentioned in Section 1, the methods presented here could inform more detailed approaches to calculating anharmonicities for only the modes most aligned with cation migration directions. Calculating the phonon-related features in this work required tens of DFT calculations for each material, which may prove too computationally expensive for computationally screening large databases of materials. Perturbative methods for estimating matrix eigenvalues and eigenvectors, 107 for example using a combination of DFT and classical force-field evaluations, could enable reductions in this computational