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arXiv 1812.03384cond-mat.mtrl-sci
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S $_x$ Se $_{1-x}$ H $_3$的热力学和超导电性

Thermodynamics and superconductivity of S$_x$Se$_{1-x}$H$_3$

Maximilian Amsler

发表信息：
Phys. Rev. B 99, 060102 (2019)
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摘要：

SH $_2$的压缩及其随后分解为SH $_3$，可能是立方Im $\overline{3}$ m结构，导致了迄今为止测量和确认的最高$T_c$的常规超导性的发现，在160 GPa下为203 K。最近的理论研究表明，S与硫族其他元素的混合物可以提高超导温度。在这里，我们提出了一个详细的分析的热力学性质的S和Se的混合物在体心立方晶格与Im $\overline{3}$ m对称性使用集团展开技术，探索相图S $_x$硒$_{1-x}$ H $_{3}$。与以前的报道相反，我们发现S $_{0.5}$ Se $_{0.5}$ H $_3$在150-200 GPa的压力范围内是不稳定的。然而，组成为S $_{0.2}$ Se $_{0.8}$ H $_3$、S $_{0.\overline{3}}$ Se $_{0.\overline{6}}$ H $_3$和S $_{0.6}$ Se $_{0.4}$ H $_3$的相在200 GPa下是稳定的，而组成为S $_{0.25}$ Se $_{0.75}$ H $_3$和S PDMATHABSe $_{0.25}$ H $_3$的另外的相在较低压力下是可获得的。电子-声子计算表明，$T_c$的值始终较低的所有三元相，表明S和Se与H的混合物可能不是一个可行的路线，以改善超导性能的化合物。

英文摘要：

The compression of SH$_2$ and its subsequent decomposition to SH$_3$, presumably in a cubic Im$\overline{3}$m structure, has lead to the discovery of conventional superconductivity with the highest measured and confirmed $T_c$ to date, 203 K at 160 GPa. Recent theoretical studies suggest that a mixture of S with other elements of the chalcogen group could improve the superconducting temperature. Here, we present a detailed analysis of the thermodynamic properties of S and Se mixtures in the bcc lattice with Im$\overline{3}$m symmetry using a cluster expansion technique to explore the phase diagram of S$_x$Se$_{1-x}$H$_{3}$. In contrast to earlier reports, we find that S$_{0.5}$Se$_{0.5}$H$_3$ is not stable in the pressure range between 150-200 GPa. However, phases at compositions S$_{0.2}$Se$_{0.8}$H$_3$, S$_{0.\overline{3}}$Se$_{0.\overline{6}}$H$_3$, and S$_{0.6}$Se$_{0.4}$H$_3$ are stable at 200 GPa, while additional phases at S$_{0.25}$Se$_{0.75}$H$_3$ and S$_{0.75}$Se$_{0.25}$H$_3$ are accessible at lower pressures. Electron-phonon calculations show that the values of $T_c$ are consistently lower for all ternary phases, indicating that mixtures of S and Se with H might not be a viable route towards compounds with improved superconducting properties.

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