Divergent synthesis routes and superconductivity of ternary hydride MgSiH6 at high pressure

Abstract

We predict a new ternary hydride MgSiH6 under high pressures, which is a metal with an ionic feature and takes on a simple cubic structure with space group Pm−3 above 250 GPa. Our first-principles calculations show that the cubic MgSiH6 is a potential high-temperature superconductor with a superconducting transition temperature Tc of ∼63 K at 250 GPa. Further analysis suggests that phonon softening along mainly Γ−X and Γ−M directions induced by Fermi surface nesting plays a crucial role in the high-temperature superconductivity. Herein we propose the “triangle straight-line method” which provides a clear guide to determine the specific A + B → D type formation routes for ternary hydrides of the Mg-Si-H system and it effectively reveals two divergent paths to obtain MgSiH6 under high pressures: MgH2+SiH4→MgSiH6 and MgSi + 3H2→MgSiH6. This method might be applicable to all ternary compounds, which will be very significant for further experimental synthesis.

Source-reported materials — not catalogue approval

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