Ternary superconducting hydrides stabilized via Th and Ce elements at mild pressures

The discovery of covalent H_(3)S and clathrate structure LaH_(10) with excellent superconducting critical temperatures at high pressures has facilitated a multitude of research on compressed hydrides.However,their superconducting pressures are too high(generally above 150 GPa),thereby hindering their application.In addition,making room-temperature superconductivity close to ambient pressure in hydrogen-based superconductors is challenging.In this work,we calculated the chemically“pre-compressed”Be-H by heavy metals Th and Ce to stabilize the superconducting phase near ambient pressure.An unprecedented ThBeH_(8)(CeBeH_(8))with a“fluorite-type”structure was predicted to be thermodynamically stable above 69 GPa(76 GPa),yielding a T_(c) of 113 K(28 K)decompressed to 7 GPa(13 GPa)by solving the anisotropic Migdal–Eliashberg equations.Be-H vibrations play a vital role in electron–phonon coupling and structural stability of these ternary hydrides.Our results will guide further experiments toward synthesizing ternary hydride superconductors at mild pressures.