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arXiv 1407.2000cond-mat.mtrl-sciphysics.comp-ph
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Be-H系统中稳定化合物、晶体结构和超导电性的探索

Exploration of stable compounds, crystal structures, and superconductivity in the Be-H system

Shuyin Yu, Qingfeng Zeng, Artem R. Oganov, Chaohao Hu, Gilles Frapper, Litong Zhang

摘要:

采用第一性原理变组分演化方法,我们探索了铍铍青铜在0和400 GPa之间的高压结构。我们发现,BeH $_2$仍然是唯一稳定的化合物在此压力范围内。压力诱导的转变被预测为$Ibam$ $\rightarrow $ $P\bar{3}m1$ $\rightarrow $ $R\bar{3}m$ $ \rightarrow $ $Cmcm$ $ \rightarrow $ $P4/nmm$,它们分别发生在24、139、204和349 GPa。$P\bar{3}m1$和$R\bar{3}m$结构是基于H原子与Be原子在交替层中填充八面体空隙的紧密堆积的层状多型体。$Cmcm$和$P4/nmm$结构具有强键的三维网络,但也分别具有矩形和方形H原子层,具有短H-H距离。$P\bar{3}m1$和$R\bar{3}m$是半导体,而$Cmcm$和$P4/nmm$是金属。我们已经探索了两种金属相的超导电性,并发现大的电子-声子耦合参数$ λ$ =0.63的$Cmcm$(导致$T_c$为32.1-44.1 K)在250 GPa和$ λ$ =0.65的$P4/nmm$($T_c$ = 46.1-62.4 K)在400 GPa。$T_c$对压力的依赖性表明,$T_c$最初增加到最大值45.1 K的$Cmcm$在275 GPa和97.0 K的$P4/nmm$在365 GPa,然后随着压力的增加而降低。

英文摘要:

Using first-principles variable-composition evolutionary methodology, we explored the high-pressure structures of beryllium hydrides between 0 and 400 GPa. We found that BeH$_2$ remains the only stable compound in this pressure range. The pressure-induced transformations are predicted as $Ibam$ $\rightarrow $ $P\bar{3}m1$ $\rightarrow $ $R\bar{3}m$ $ \rightarrow $ $Cmcm$ $ \rightarrow $ $P4/nmm$, which occur at 24, 139, 204 and 349 GPa, respectively. $P\bar{3}m1$ and $R\bar{3}m$ structures are layered polytypes based on close packings of H atoms with Be atoms filling octahedral voids in alternating layers. $Cmcm$ and $P4/nmm$ structures have 3D-networks of strong bonds, but also feature rectanular and squre, respectively, layers of H atoms with short H-H distances. $P\bar{3}m1$ and $R\bar{3}m$ are semiconductors while $Cmcm$ and $P4/nmm$ are metallic. We have explored superconductivity of both metallic phases, and found large electron-phonon coupling parameters of $ λ$=0.63 for $Cmcm$ (resulting in a $T_c$ of 32.1-44.1 K) at 250 GPa and $ λ$=0.65 for $P4/nmm$ ($T_c$ = 46.1-62.4 K) at 400 GPa. The dependence of $T_c$ on pressure indicates that $T_c$ initially increases to a maximum of 45.1 K for $Cmcm$ at 275 GPa and 97.0 K for $P4/nmm$ at 365 GPa, and then decreases with increasing pressure for both phases.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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