Predicting the stability of the hydride and hydrogen embedding ways based on the characteristics of the electron localization function

Previous studies have shown that the electron occupation of local quasi-atomic orbitals and their corresponding chemical interactions determine the structural preference of materials under pressure. In metal super-hydrides, when H atoms are removed, the remaining metal sublattices exhibit characteristics of interstitial quasi-atomic (ISQ) orbitals occupied by electrons. In this paper, 124 kinds of systems (including AHCu₃ and MgHE₃) are constructed by replacing Mg atoms with A atoms or replacing Cu atoms with E atoms in the MgHCu₃ system. By systematically studying the intrinsic relationship between the superconductivity and stability of these systems and their electronic structures, three strategies are proposed for screening stable structures or optimizing the superconductivity of the system efficiently. (1) Stability rapid screening strategy: We establish an effective stability criterion based on the matching between the electron localization function (ELF) characteristics of the replacement system and the parent system, and its prediction accuracy reaches up to 76 %. This result provides a reliable electronic structure basis for the prediction of superconductor stability, which can improve the screening efficiency of stable structures. (2) Hydrogen atom embedding strategy: “Chemical templates that assemble the metal super-hydrides”, based on this idea, we propose a reverse design strategy for hydrogen-rich superconductors by using three different hydrogen embedding methods based on the ELF characteristics of the metal lattice, nine new hydride superconductors are successfully designed, including MgH₄Cu₃, PdH₄Cu₃, NaH₄Cu₃, AgH₄Cu₃, LiH₄Cu₃, MgH₄Na₃, Cu₄H₄, MgH₇Ba₃, and Mg₄H₉. Among them, Mg₄H₉ has a T_c of 84.4 K at 20 GPa, and MgH₇Ba₃ has a T_c of 54.8 K at 50 GPa. (3) Strain control strategy: By applying 5 % tensile strain to the MgHNa₃ system, its T_c was successfully increased from 16.4 K to 28.4 K. This strategy applies to superconductors whose superconductivity is negatively correlated with pressure and are stable at ambient pressure. These strategies not only provide a new theoretical method for the structural design of hydride superconductors and the rapid screening of stable structures, but also open up new ideas for the optimization of superconductivity.