“…16,20,21,36,39 The breathing mode is mainly influenced by the anion substitution and to a minor extent by the A cation. 37,38 Regarding the B and E modes, their strong cation dependence, mainly in the low and highfrequency regions, has allowed to understand the different vibrations that occur inside the unit cell. 40,41 In fact, the substitution of A (B) cations in OVCs has revealed a one-mode (two-mode) behavior of the low-frequency (high-frequency) vibrational modes.…”