High-pressure Mg-Sc-H phase diagram and its superconductivity from first-principles calculations

TL;DR

This study uses first-principles calculations to explore the high-pressure phase diagram of Mg-Sc-H hydrides, identifying stable structures and predicting their superconducting properties, with the highest transition temperature around 23.34 K.

Contribution

The paper presents a comprehensive first-principles analysis of Mg-Sc-H hydrides under high pressure, discovering new stable phases and predicting their superconducting transition temperatures.

Findings

Identified four thermodynamically stable Mg-Sc-H compounds at high pressure.

Predicted superconducting transition temperatures up to 23.34 K.

Mapped the pressure-dependent phase diagram of Mg-Sc-H hydrides.

Abstract

In this work, global search for crystal structures of ternary Mg-Sc-H hydrides (Mg$_x$Sc$_y$H$_z$) under high pressure ($100 \le P \le 200$ GPa) were performed using the evolutionary algorithm and first-principles calculations. Based on them, we computed the thermodynamic convex hull and pressure-dependent phase diagram of Mg$_x$Sc$_y$H$_z$ for $z/(x+y) < 4$. We have identified the stable crystal structures of four thermodynamically stable compounds with the higher hydrogen content, i.e., $R\bar{3}m$-MgScH$_{6}$, $C2/m$-Mg$_{2}$ScH$_{10}$, $Immm$-MgSc$_{2}$H$_{9}$ and $Pm\bar{3}m$-Mg(ScH$_{4}$)$_{3}$. Their superconducting transition temperatures were computationally predicted by the McMillan-Allen-Dynes formula combined with first-principles phonon calculations. They were found to exhibit superconductivity; among them, $R\bar{3}m$-MgScH$_{6}$ was predicted to have the highest $T_{c}$ (i.e. 23.34 K) at 200 GPa.