Superconductivity of ternary XBeH8 hydrides (X = La, Ba, Pr, Ac) under high pressure

Abstract

Although extensive studies have been conducted on binary hydrides, an ideal superconductor at ambient temperature and pressure has yet to be discovered. Ternary hydrides increase the possibility of different crystal structures exponentially and can make up for the poor stability and the disadvantage of low Tc caused by the single doping element (X) in binary hydrides (XHn). In this work, we systematically studied the structural stability, bonding properties, electronic structure, electron-phonon coupling and superconducting properties of the XBeH8 (X=La, Ac, Ba, Pr) system within the pressure of 0-500 GPa. First, phonon spectra were used to determine the stability regimes influenced by different X elements. Second, we analyzed the atomic interactions based on the electronic structure. We further calculated the electron-phonon coupling and superconducting properties of the stable structures. The Tc of AcBeH8 (LaBeH8) was calculated to reach 142 K at 50 GPa (137 K at 20 GPa). Furthermore, the Fm3-m phase of PrBeH8 is reported for the first time. It exhibits a large λ of 3.27 at 30 GPa, with a predicted Tc of 148 K. Additionally, PrBeH8 is predicted to reach a Tc of 215 K under 400 GPa.