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

Abstract

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.

Pressure‐induced lattice‐dynamical stability and superconductivity of ternary pentahydride MgNiH 5

“…32 Also, very recently, Mg-substituted systems have led to predictions of ternary Mg-Sc-H phase. 30 These findings apparently indicate the crystal structure of MgScH 6 shows superconductivity with T c of 41 K at a pressure of 100 GPa. Apart from superconductivity in Hrich materials, carbonaceous sulfur hydride (C-S-H) emerges as a promising candidate in the high-pressure society as it is demonstrated in the experiment to be superconducting at a T c approaching room temperature.…”

“…It is, moreover, worth noting that magnesium has the potential to form an H‐rich phase, that is, the sodalite‐like MgH 6 is stable above 263 GPa 32 . Also, very recently, Mg‐substituted systems have led to predictions of ternary Mg‐Sc‐H phase 30 . These findings apparently indicate the crystal structure of MgScH 6 shows superconductivity with T c of 41 K at a pressure of 100 GPa.…”

“…Interestingly, ternary metal hydrides were also extensively studied. 19,[27][28][29][30][31] The idea of ternary alloys puts forward another promising direction as it involves a fairly large number of possible decorations of metal atoms with hydrogen. One of the most reliable of doing so is the atomistic simulation based on the particle swarm optimization method, by which the superconductivity in Li-Mg-H system was observed.…”

Potential high-$T_{c}$ superconductivity in YCeH$_{20}$ and LaCeH$_{20}$ under pressure

“…But then multi-component hydrides contain more combinations of elements, they are more promising in the search for high(room)-temperature superconductivity. [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59] For example, magnesium hydride can dissociate the H 2 molecule into atomic H by lithium doping, thus increasing its electron concentration at the Fermi level (E F ), enabling it to reach a T c value of 473 K at 250 GPa. [47] Furthermore, recent research has revealed that a small amount of carbon doping in H 3 S can result in room superconductivity (T c = 287.7 ± 1.2 K at 267 ± 10 GPa).…”

(La,Th)H$_{10}$: the potential high-$T_{c}$ superconductors stabilized thermodynamically below 200 GPa

“…Recently, the superconductivity of ternary clathrate hydride has also attracted a lot of attention, and most of them cover the hydrides of alkaline-earth metals and rare-earth metals. [9,[31][32][33][34][35][36][37][38][39][40][41] Although the theoretically predicted T c of Li 2 MgH 16 composed of alkali and alkaline-earth metals at 250 GPa is 473 K, its enthalpy of formation lies above the convex hull [8,42] and its synthesis in experiment is still a great challenge. It is noteworthy to mention that partial replacement of La atoms by magnetic Nd atoms results in significant suppression of superconductivity in LaH 10 .…”