高压下三元富氢化合物Ac-Zr-H的结构及超导电性研究

Due to its excellent properties of zero resistance and magnetic resistance, superconducting materials have a wide range of applications in the fields of energy, industry and military. However, the practical applications are still limited by the factors such as the low transition temperature (Tc), so it is an important task to find the new type of superconductors with higher Tc. Hydrogen-rich compounds are a high potential high-temperature superconducting materials in conventional superconductors. Great progresses have been achieved in both theoretical and experimental researches in recent years. For transition metals and actinides, the d/f-orbit electrons contribute to the high electron density near the Fermi level which will possibly lead to the enhancement of transition temperature. Therefore, we intend to perform theoretical simulations based on particle swarm optimization (PSO) algorithm with the first principle calculations in the Ac-Zr-H system. With such a systematic investigation on the lattice and electronic structure of the system under high pressure, we might be able to draw the phase diagram of this system, and acquire new potential high-temperature superconductors. Furthermore, the mechanism of the superconductivity will be explored, which shall provides theoretical support and a thorough understanding of this new transition metal/actinides hydrides material.

超导材料由于具有零电阻、抗磁性的优异特性，在能源、工业和军事等领域具有丰富的应用前景，然而其实际应用仍受到超导转变温度(Tc)过低等因素的制约，因此寻找具有较高Tc的新型超导体是凝聚态物理前沿研究的重要课题。. 富氢化合物是传统超导体中非常有潜力的一类高温超导材料，近年来其在理论和实验上的研究均取得了很大的进展。对于过渡金属和锕系元素，其d/f轨道电子在费米面附近的高电子态密度贡献可能有利于提高超导体转变温度。因此本项目拟设计Ac-Zr-H三元富氢化合物，通过基于粒子群优化算法的结构预测技术结合高精度第一性原理计算，系统地研究其在高压下的晶格和电子行为，以期获得体系的高压相图，寻找到潜在的新型高温超导材料，进而探寻其超导机制，为研究富氢化合物的超导电性提供新的理论支持和认识。

寻找具有较高超导转变温度的新型超导材料是当前物理与材料领域倍受关注的重要研究课题。根据传统BCS超导理论， 富氢体系化合物被认为是实现氢金属化并寻找室温超导体的重要候选材料。本项目通过基于密度泛函理论的第一性原理从头算方法，对Zr-Ac-H三元体系在高压条件下展开系统研究，结果表明了两种稳定的基态化合物，空间群对称性为F4_132的ZrAcH6（80~210GPa）和化学配比为ZrAcH16（>173GPa)的P4/mmm的四方晶格，特别的，在ZrAcH16里，H原子形成接近正方形的H4集团。这俩种三元化合物均表现了良好的金属特性，其中ZrAcH16在费米面处的高态密度显示了其潜在的优异超导特性。电声耦合计算结果表明，ZrAcH16是一个潜在的高温超导体，其在200GPa下超导转变温度可以达到167K。该结果证明了在三元富氢化合物中寻找室温超导体的可能性。

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