3-ions and exhibits pseudo-rotation at RT. The study also found the existence of pseudo-rotation in other complex transition metal hydrides containing OsH within this class of materials, Li 6 NbH 11 deserves attention, as it features Li + ions exhibiting several meta-stable sites, which implies a lower hopping barrier for Li + and a facile Li + ion conduction (79 mS cm -1 RT ). The high anion rotation may cause structural instability, while the immobile H - ions can increase the structural stability. However, a comprehensive investigation is needed to validate the theoretically calculated ionic conductivity and associated speculation.