Stability and superconductivity of hexagonal prism-structured polyhydrides X2MgH18 (X = Li, Na, K, Rb, Cs) under moderate pressure

We searched for compounds X 2 MgH 18 (X = Li, Na, K, Rb, Cs) and identified Li 2 MgH 18 as dynamically stable and superconducting at 20 GPa (110 K) and 235 GPa (122 K). The distortion of its hexagonal prism structure enhances the critical temperature ( T c ).