High-Pressure Mg–Sc–H Phase Diagram and Its Superconductivity from First-Principles Calculations

• Published in: Journal of physical chemistry. C Vol. 126; no. 5; pp. 2747 - 2755
• Main Authors: Song, Peng, Hou, Zhufeng, Baptista de Castro, Pedro, Nakano, Kousuke, Hongo, Kenta, Takano, Yoshihiko, Maezono, Ryo
• Format: Journal Article
• Language: English
• Published: American Chemical Society 10-02-2022
• Subjects: C: Physical Properties of Materials and Interfaces
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.1c08743

In this work, a global search for crystal structures of ternary Mg–Sc–H hydrides (Mg x Sc y H z ) under high pressure (100 ≤ P ≤ 200 GPa) was performed using the evolutionary algorithm and first-principles calculations. On their basis, we computed the thermodynamic convex hull and pressure-dependent phase diagram of Mg x Sc y H z for a wide range of compositions (x + y = 2, 3, 4 and z = 2–12, 14, 16, 18). Our crystal structure search and convex hull analysis revealed no thermodynamically stable compounds in the hydrogen-rich range (z/(x + y) ⩾ 4). On the other hand, we identified the crystal structures of four thermodynamically stable compounds in the hydrogen-middle range (3 ≤ z/(x + y) < 4), that is, R3̅m-MgScH6, C2/m-Mg2ScH10, Immm-MgSc2H9, and Pm3̅m-Mg­(ScH4)3. Their superconducting transition temperatures were computationally predicted by the McMillan formula combined with first-principles phonon calculations. They were found to exhibit superconductivity; among them, R3̅m-MgScH6 was predicted to have the highest T c (i.e., 41 K) at 100 GPa.