Design of High‐Tc Quaternary Hydrides Under Moderate Pressures Through Substitutional Doping

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AbstractIn recent years, there has been considerable interest in exploring high‐temperature superconductors in hydrides at low‐pressure conditions. A series of quaternary XAZ2H16 compounds (X, A = La, Ca, Sr, Ba, Ac, Ce, Th, Na or K; Z = Be, B, Si or P) are constructed based on ternary Fm‐3m LaB/BeH8‐type structure. Eight hydrides are found to be thermodynamically stable, with LaThBe2H16 and AcBaSi2H16 exhibiting lower pressures of 92 and 81 GPa, respectively. All investigated hydrides display dynamical stability at pressures below one million atmospheres, with LaThBe2H16 remaining stable even as low as 8 GPa. Moreover, LaSrB2H16, AcBaSi2H16, AcSrSi2H16, and Ba2SiPH16 exhibit clear covalent bonding characteristics between Z and H atoms, while Be atoms tend to form ionic bonds with H atoms. Electron‐phonon coupling calculations indicate that all of these quaternary hydrides have potential as superconductors. LaThBe2H16, AcBaSi2H16, AcSrSi2H16 and YCeBe2H16 exhibit superconducting transition temperatures (Tcs) of 126, 137, 123, and 104 K at 10, 30, 30, and 45 GPa, respectively, while LaYBe2H16 exhibits the highest Tc of 221 K at 75 GPa. These findings provide valuable insights for the search for high‐Tc superconductors under lower pressure conditions and encourage further exploration of polynary superconducting hydrides.