For half a century after the discovery of superconductivity, materials exploration for better superconductors proceeded without knowledge of the underlying mechanism. The 1957 BCS theory cleared that up. The superconducting state occurs due to strong correlation in the electronic system: pairing of electrons over the Fermi surface. Over the following half century a higher critical temperature $T_c$ was achieved only serendipitously as new materials were synthesized. Meanwhile, the formal theory of phonon-coupled superconductivity at the material-dependent level became progressively more highly developed: by 2000, given a known compound, its value of $T_c$, the corresponding superconducting gap function, and several other properties of the superconducting state became available independent of further experimental input. In this century, density-functional-theory-based computational materials design has progressed to a predictive level; new materials can be predicted from free energy functionals on the basis of various numerical algorithms. Taken together these capabilities enable theoretical predictions for new superconductors, justified by applications to superconductors ranging from weak to strong coupling. Limitations of the current procedures are discussed; most of them can be handled with additional procedures. Here the process that has resulted in the three new highest temperature superconductors is recounted, with compressed structures predicted computationally and values of $T_c$ obtained numerically that have subsequently been confirmed experimentally: the designed superconductors ${\mathrm{SH}}_3$, ${\mathrm{LaH}}_{10}$, and ${\mathrm{YH}}_9$. These hydrides have $T_c$ in the 200–260 K range at megabar pressures; the experimental results and confirmations are discussed. While the small mass of hydrogen provides the anticipated strong coupling at high frequency, it is shown that it also enables identification of the atom-specific contributions to coupling, in a manner that was previously possible only for elemental superconductors. The following challenge is posed: that progress in understanding of higher $T_c$ is limited by the lack of understanding of screening of H displacements. Ongoing activities are mentioned and current challenges are suggested, together with regularities that are observed in compressed hydrides that may be useful to guide further exploration.

中文翻译：

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研讨会：室温超导：理论和材料设计的作用

在发现超导性后的半个世纪里，人们对更好的超导体的材料探索一直在进行，而对其潜在机制却一无所知。 1957 年的 BCS 理论澄清了这一点。超导态的发生是由于电子系统中的强相关性：费米表面上的电子配对。在接下来的半个世纪里，临界温度更高${\mathrm{时间}}_C$随着新材料的合成，这一结果只是偶然实现的。与此同时，材料相关水平上的声子耦合超导正式理论逐渐得到高度发展：到 2000 年，给定一种已知化合物，其值${\mathrm{时间}}_C$、相应的超导能隙函数以及超导态的其他几个性质都可以独立于进一步的实验输入而获得。本世纪，基于密度泛函理论的计算材料设计已经发展到了预测水平。可以根据各种数值算法从自由能泛函预测新材料。总而言之，这些功能可以对新型超导体进行理论预测，并通过从弱耦合到强耦合的超导体应用来证明其合理性。讨论了当前程序的局限性；其中大多数可以通过额外的程序来处理。这里叙述了产生三种新的最高温度超导体的过程，其中包括计算预测的压缩结构和值${\mathrm{时间}}_C$获得的数值随后被实验证实：设计的超导体${\mathrm{SH}}_3$,${\mathrm{卤化氢}}_{10}$， 和${\mathrm{玉华}}_9$。这些氢化物具有${\mathrm{时间}}_C$兆巴压力下 200–260 K 范围内；讨论了实验结果和验证。虽然小质量的氢在高频下提供了预期的强耦合，但研究表明，它还能够以以前仅对元素超导体才有可能的方式识别原子特定对耦合的贡献。提出了以下挑战：在理解更高层次的知识方面取得进展${\mathrm{时间}}_C$由于缺乏对 H 位移筛选的了解而受到限制。提到了正在进行的活动并提出了当前的挑战，以及在压缩氢化物中观察到的规律，这些规律可能有助于指导进一步的勘探。