Abstract
Inspired by the diverse properties of sulfur hydrides and phosphorus hydrides, we combine first-principles calculations with structure prediction to search for stable structures of Li−P−H ternary compounds at high pressures with the aim of finding novel superconductors. It is found that phosphorus hydrides can be stabilized under pressure via additional doped lithium. Four stable stoichiometries LiPH3, LiPH4, LiPH6, and LiPH7 are uncovered in the pressure range of 100–300 GPa. Notably, we find an atomic LiPH6 with Pmoverline 3 symmetry which is predicted to be a potential high-temperature superconductor with a Tc value of 150–167 K at 200 GPa and the Tc decreases upon compression. All the predicted stable ternary hydrides contain the P–H covalent frameworks with ionic lithium staying beside, but not for Pmoverline 3-LiPH6. We proposed a possible synthesis route for ternary lithium phosphorus hydrides: LiP + H2 → LiPHn, which could provide helpful and clear guidance to further experimental studies. Our work may provide some advice on further investigations on ternary superconductive hydrides at high pressure.
Highlights
Given the metallization and potential room temperature superconductivity of solid hydrogen under high pressure have been proposed,[1,2] considerable efforts have been exerted in finding metallic hydrogen
Experimental observations of the metallic hydrogen phase remain controversial, researchers have agreed that hydrogen requires considerable high pressure to reach the metallic state
250 GPa, LiPH6 is thermodynamically stable with Pm3 symmetry, which is isostructural with ternary hydrides MgSiH6 and MgGeH6.39,40 Pm3-LiPH6 is calculated to be a potential high-Tc superconductor with Tc about 150–167 K at 200 GPa and the Tc reduces with pressure increasing
Summary
Given the metallization and potential room temperature superconductivity of solid hydrogen under high pressure have been proposed,[1,2] considerable efforts have been exerted in finding metallic hydrogen. We try to dope lithium into the P–H system, and expect to find the stable hydrogen-rich ternary compounds with potential high-temperature superconductivity.
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