As previously highlighted, a comprehensive understanding of the factors influencing the diminishment of rotational activation energy (E r a ) is imperative for stabilizing the high-conductivity phase in complex hydrides at RT. In this regard, we have identified cell expansion as a pivotal factor in modulating anion-cation interactions. Notably, at the T tran , a sharp transition in the unit cell volume (V ) takes place, enabling the anionic and cationic species to move farther apart from each other. This phenomenon leads to a weakening of their mutual interactions or the release of the trapping constraints imposed by the cations, thus affording greater spatial freedom for enhanced anion rotation, as visually depicted in Fig. ). Furthermore, it is worth noting that the strength of cationic trapping can also be mitigated through deliberate modifications.