Consequently, low-frequency modes differ in the extent to which they involve motion of the migrating cation rather than the anions (Figures and). Analyzing the extent to which each mode involves cation motions and the directions of these motions may therefore provide insight into the lack of correlation in Figure . A framework for analyzing the alignment of phonon eigenvectors with ion migration directions was described by Gordiz et al., who focused on the Li-ion conductor Li 3.042 Ge 0.042 P 0.958 O 4 .