paper

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

arXiv:2109.07051 · doi:10.1021/acs.jpcc.1c08743

Abstract

In this work, global search for crystal structures of ternary Mg-Sc-H hydrides (Mg $_{x}$ Sc $_{y}$ H $_{z}$ ) under high pressure ( $100 \leq P \leq 200$ 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., $R 3 ˉ m$ -MgScH $_{6}$ , $C 2/ m$ -Mg $_{2}$ ScH $_{10}$ , $I mmm$ -MgSc $_{2}$ H $_{9}$ and $P m 3 ˉ m$ -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, $R 3 ˉ m$ -MgScH $_{6}$ was predicted to have the highest $T_{c}$ (i.e. 23.34 K) at 200 GPa.

7 pages, 5 figures, 1 Supplemental Material