Design of High-Tc LiMgM2H12 Quaternary Hydrides Via Atomic Substitution over a Wide Pressure Range

Hydrogen-rich hydrides are promising candidates for high-temperature superconductivity within the framework of conventional phonon-mediated Bardeen–Cooper–Schrieffer (BCS) theory. However, the structural stability of these systems typically requires extreme pressures, which severely limits their practical applications. Consequently, considerable research effort has been devoted to identifying hydride superconductors that can remain stable and superconducting at lower pressures. Building on our previous study of LiMgZr2H12 at ambient pressure, we constructed a series of LiMgM2H12 structures with Pmmm symmetry through atomic substitution. High-throughput screening based on first-principles calculations was subsequently performed at pressures of 0, 20, 50, 100, and 200 GPa. Ultimately, nine dynamically stable structures were identified: LiMgM2H12 (M = Zr, Hf, Nb, Ta, Sn, Ti, V, As, and P). All nine compounds are predicted to be superconducting. Notably, LiMgHf2H12 and LiMgTa2H12 exhibit high superconducting critical temperatures of 104.9 and 90.4 K, respectively, at a relatively low pressure of 50 GPa. More importantly, our results suggest that early transition metals, especially 4d and 5d elements from groups IVB and VB, are more favorable for achieving higher Tc values at lower pressures. This work elucidates how elemental substitution tunes the structural stability and superconducting properties of the LiMgM2H12 series and provides theoretical guidance for designing new multicomponent hydrogen-rich superconductors.