The Systematic Study on the Stability and Superconductivity of Y‐Mg‐H Compounds under High Pressure
The Systematic Study on the Stability and Superconductivity of Y‐Mg‐H Compounds under High Pressure
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Y-Mg-H化合物高压稳定性和超导性的系统研究
DOI：
10.1002/adts.202100364
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发表时间：
2021-07
影响因子：
3.3
通讯作者：
Peng Song;Z. Hou;P. D. de Castro;K. Nakano;Y. Takano;R. Maezono;K. Hongo
中科院分区：
文献类型：
--
作者：
Peng Song;Z. Hou;P. D. de Castro;K. Nakano;Y. Takano;R. Maezono;K. Hongo
采用基于进化算法的晶体搜索结合第一性原理计算研究了高压YMgHx相（x=2− 10，12，14$x = 2-10，12，14$，和16）的结构稳定性及其超导性.对于预测的候选结构的YMgHx，凸船体和声子分析揭示七个稳定和两个亚稳阶段。对于所有预测的相位，超导转变温度（Tc）也预测通过使用McMillan公式。发现P4/mmm$P4/mmm$-YMgH 6在300 GPa下具有与液氮的沸腾温度相当的Tc= 76 $T_\mathrm {c} = 76$ K，并且对于更富H的相P4/mmm$P4/mmm$-YMgH 8预测高Tc（≥77 K（124 K，300 GPa）、Cmmm$Cmmm$-YMgH 12（152 K，250 GPa）和Fd 3 <$m$Fd\bar{3}m$-YMgH 12（190 K，200 GPa），它们分别具有由H14、H18、H24和H24笼组成的笼形结构。为了阐明富氢相获得高Tc的原因，基于Eliashberg光谱函数分析了电子和声子能带结构以及电子-声子耦合强度。笼形结构在费米能级处表现出更大的H驱动电子态密度和更密集的H驱动声子态密度，这与更大的EPC常数相关。这些结构和化学键分析表明，最高的-Tc相Fd 3 <$m$Fd\bar{3}m$-YMgH 12具有在方钠石笼中形成的H4单元。
Structural stabilities of high‐pressure YMgHx phases ( x=2−10,12,14$x = 2-10, 12, 14$ , and 16) and their superconductivities are investigated by employing evolutionary‐algorithm‐based crystal search combined with first‐principles calculations. For predicted candidate structures of YMgHx, the convex hull and phonon analyses reveal seven stable and two metastable phases. For all the predicted phases, superconducting transition temperatures (Tc) are also predicted by using the McMillan formula. P4/mmm$P4/mmm$ ‐YMgH6 is found having Tc=76$T_\mathrm{c} = 76$ K at 300 GPa comparable to the boiling temperature of liquid nitrogen, and high‐Tc (≥77 K) being predicted for the H‐richer phases, P4/mmm$P4/mmm$ ‐YMgH8 (124 K at 300 GPa), Cmmm$Cmmm$ ‐YMgH12 (152 K at 250 GPa), and Fd3¯m$Fd\bar{3}m$ ‐YMgH12 (190 K at 200 GPa), which possess clathrate structures composed of H14, H18, H24, and H24 cages, respectively. To elucidate why the H‐rich phases attain high‐Tc, electronic and phonon band structures as well as electron–phonon coupling strength are analyzed based on Eliashberg spectral functions. The clathrate structures exhibit both a larger H‐driven electronic density of states at the Fermi level and a denser H‐driven phonon density of states, correlating with larger EPC constants. These structural and chemical bonding analyses reveal that the highest‐Tc phase Fd3¯m$Fd\bar{3}m$ ‐YMgH12 has H4 units formed in the sodalite cage.