Pressure-induced superconductivity in alkaline earth metal halides MgaXb (X = Br, I) from first principles calculations

Abstract

In the field of superconductivity research, metal hydrides have emerged as a prominent area of study. Halogen elements, due to their similar electron configurations to hydrogen, make the high-pressure exploration of metal halides equally crucial. Motivated by the high superconductivity of the non-hydrogen-based superconductor MgB₂ under atmospheric pressure, we investigated the high-pressure interactions between the alkaline earth metal magnesium (Mg) and halogens (Br, I) using density functional theory (DFT). A comprehensive analysis is conducted on the high-pressure phase diagrams, bonding properties, electronic characteristics, and superconductivity of the metal halides Mg_aX_b (X = Br, I). Our results reveal that, for alkaline earth metal halides Mg_aX_b (X = Br, I), phonon softening could lightly enhance the electron–phonon coupling constant λ, thereby improving superconducting properties, while the excessive appearance of interstitial charge and the predominance of low-frequency acoustic branches in electron–phonon coupling are detrimental to superconductivity.