The Systematic Study on the Stability and Superconductivity of Y?Mg?H Compounds under High Pressure

Motivated by recent discovery of yttrium-based high-temperature ternary superconducting hydrides (e.g., CaYH$_{12}$, LaYH$_{12}$, and ScYH$_{6}$), we have employed evolutionary algorithm first-principles calculations to comprehensively examine the structural stability superconductivity YMgH$_{x}$ system at high pressure. The hydrogen content $x$ pressure are both important factors in these candidate structures. We find that hydrogen-rich materials frequently necessitates higher For instance, pressures stabilize $P4/mmm$-YMgH$_{8}$ $Cmmm$-YMgH$_{12}$ more than 250 GPa. Hydrogen-less materials, such as $I4_{1}/amd$-YMgH$_{2}$ $P6_{3}/mmc$-YMgH$_{3}$, can be stable low 100 In addition, a metastable structure for YMgH$_{6}$ with same space group $P4/mmm$-YMgH$_{8}$. A sodalite-like face-centered cubic (FCC) is also found YMgH$_{12}$. These four clathrate structures $P4/mmm$-YMgH$_{6}$, $P4/mmm$-YMgH$_{8}$, $Cmmm$-YMgH$_{12}$, $Fd\bar{3}m$-YMgH$_{12}$ made up H14, H18, H24, H24 cages, respectively, which H-H pair exhibits weak covalent bonding. According phonon calculations, $P4/mmm$-YMgH$_{6}$ require 300 GPa maintain dynamic stability, however 200 GPa, respectively. Electron-phonon coupling indicate they might potential superconductors, intimately linked H cage structure. sodalite has $T_\mathrm{c}$ value 190 K strong electron-phonon constant 2.18.