Low-pressure superconducting properties and the regulation mechanism of the ternary hydride Li2PbH4

Abstract

Hydrogen-rich compounds are promising candidates for room-temperature superconductors; however, the requirement for extreme stabilizing pressures limits their practical applications. Using crystal structure prediction combined with first-principles calculations, this study identifies a ternary clathrate hydride Im2-Li₂PbH₄ that is stable at 34 GPa. The introduction of Li effectively dissociates H₂ molecules through substantial charge transfer and forms strong Pb–Li orbital coupling with Pb atoms. This exerts a remarkable chemical precompression effect on the three-dimensional Pb–H hydrogen cage framework, which efficiently suppresses lattice softening and structural decomposition under low pressure and stabilizes the hydrogen skeleton effectively. Meanwhile, Li doping optimizes the electronic structure and phonon vibration modes of the system, leading to significantly enhanced electron–phonon coupling. Consequently, dual improvements are achieved: reduced stabilizing pressure (34 GPa) and an elevated superconducting transition temperature (T_c) of 123 K. This confirms that introducing metal elements into binary hydrogen-rich compounds enhances EPC, enabling high superconducting performance at lower pressures. This finding provides a paradigm for designing other ternary or quaternary hydrides, suggesting that regulating complex hydrogen cage structures through metal doping is an effective strategy for exploring high-performance superconductors. This approach is expected to stimulate further experimental synthesis and research into superconducting mechanisms.