Ductile Al7MgH2 superconductors with Tc up to 64 K at ambient pressure

Abstract

Ductile high-temperature superconductors are essential for engineering applications such as superconducting tapes and wires. However, materials that simultaneously exhibit mechanical ductility and a superconducting transition temperature (Tc) above liquid nitrogen temperature remain scarce. In this study, we start with the experimentally reported Al7Mg alloy and investigate the structures, electron-phonon coupling (EPC), and superconducting properties of various Al7MgH2 configurations through first-principles calculations combined with statistical methods. Statistical analysis reveals that the percentage contribution of H density of states at the Fermi level (EF) and the H local space are two factors determining superconductivity. While the hydrogen occupation site has a negligible effect on the electronic structure, it significantly alters the phonon spectra. Specifically, the intrinsic vibrational modes of H are primarily associated with phonon frequencies, whereas the local chemical environment of H strongly influences EPC through phonon spectra softening or hardening, as demonstrated through our analysis of H phonon splitting and vibrational mode visualization. The predicted Al7MgH2 crystal can sustain superconductivity up to 64 K at ambient pressure while exhibiting excellent ductility comparable to that of Al and AlMg alloys. Our results show that AlMg-based hydrides may bridge the gap in the absence of ductile superconductors near the liquid-nitrogen temperature and offer a different perspective on how interstitial hydrogen configurations affect conventional s-wave superconductivity.

Source-reported materials — not catalogue approval

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