Designing ternary superconducting hydrides with A15-type structure at moderate pressures
Designing ternary superconducting hydrides with A15-type structure at moderate pressures
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中等压力下A15型结构三元超导氢化物的设计
DOI：
10.1016/j.mtphys.2023.101086
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发表时间：
2023
影响因子：
11.5
通讯作者：
Gao, Guoying
中科院分区：
文献类型：
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作者：
Wei, Xudong;Hao, Xiaokuan;Bergara, Aitor;Zurek, Eva;Liang, Xiaowei;Wang, Linyan;Song, Xiaoxu;Li, Peifang;Wang, Lin;Gao, Guoying
自从氢基超导体被积极考虑作为室温超导体的候选者以来，二元氢化物在理论上几乎得到了完全的探索。现在研究人员将他们的兴趣转向三元氢化物。然而，三元氢化物空间中巨大的组成和结构可能性限制了搜索效率。在此，利用先进的晶体结构搜索方法结合第一性原理计算，预计一系列具有A15型结构的三元氢化物AXH6（MgPH6、MgAsH6、CaSbH6、CaSnH6、NaSbH6和ScSiH6）可在100万个大气压左右稳定。其中，CaSnH6 的热力学稳定压力最低，为 110 GPa。 CaSbH6、CaSnH6 和 ScSiH6 可以分别在低至 41 (70)、71 (90) 和 86 (70) GPa 时动态稳定，没有（有）非谐波效应和温度效应。发现这些 A15 型结构中的氢原子与 X 原子形成弱共价键。更有趣的是，我们发现当两个非氢原子的化学价之和为六或七时，具有AXH6化学计量的三元氢化物在压力下可能呈现A15型结构。根据电子声子耦合（EPC）计算，所有这些三元氢化物都被估计为超导体。 CaSbH6、CaSnH6 和 ScSiH6 在 45、75 和 90 GPa 下的超导转变温度 (Tcs) 分别为 65、53 和 116 K，而 MgPH6 在 135 GPa 下的最高 Tco 为 148 K。我们的研究将为设计接近环境压力的高三元氢化物提供指导。
Ever since hydrogen-based superconductors have been actively considered as candidates for room-temperature superconductors, binary hydrides have been almost completely explored theoretically. Now researchers are turning their interest to ternary hydrides. However, the enormous compositional and structural possibilities in the ternary hydride space limit the search efficiency. Here, using an advanced crystal structure search method combined with first-principles calculations, a series of ternary hydrides AXH6(MgPH6, MgAsH6, CaSbH6, CaSnH6, NaSbH6and ScSiH6) with the A15-type structure are predicted to be stable at around one million atmospheres. Among them, CaSnH6presents the lowest thermodynamically stable pressure of 110 GPa. CaSbH6, CaSnH6and ScSiH6may be dynamically stable down to 41 (70), 71 (90) and 86 (70) GPa, respectively, without (with) anharmonic effects and temperature effects. Hydrogen atoms in these A15-type structures are found to form weak covalent bonds to X atoms. More interestingly, we find that ternary hydrides with the AXH6stoichiometry may assume the A15-type structure under pressure when the sum of the chemical valences of the two non-hydrogen atoms is six or seven. Based on electron-phonon coupling (EPC) calculations, all these ternary hydrides are estimated to be superconductors. CaSbH6, CaSnH6and ScSiH6have superconducting transition temperatures (Tcs) of 65, 53 and 116 K at 45, 75 and 90 GPa, respectively, while MgPH6has the highestTcof 148 K at 135 GPa. Our study will provide guidance for designing highTcternary hydrides near ambient pressures.