To determine whether features related to mode alignments with the neighboring cation Figure : Relationships between two metrics related to phonon mode frequencies and alignments with vacancy migration barriers for all materials. The two metrics are (a) the mean frequency of the 10 % of modes in each material with the greatest degree of alignment with the neighboring cation displacement field, and (b) the mean alignment-weighted frequency for the neighboring cation displacement field, defined in eq 6. The black dashed trend lines were obtained by least-squares linear regression. alignments. (Spectra of alignments for all other materials are presented in Figure .)