M-CHx（M代表碱金属、碱土金属和稀土金属）三元氢化物中低压高温超导电性的理论研究

近年来，在氢化物中观察到的接近室温的超导电性，把人们对氢化物超导体的研究兴趣推向了一个新的高潮。但是氢化物中H原子结构对超导电性的影响规律尚无定论，且高温超导电性所依附的压强仍然过高（兆帕以上），因此进一步探索氢化物的超导机理，发展低压高温超导体迫在眉睫。本项目基于第一性原理方法聚焦于兼具极性共价键和离子键的M-CHx（M代表碱、碱土和稀土金属）三元氢化物，1）研究CHx在压力和金属掺杂下的结构特征和变化规律，2）研究降低体系金属化压强的机理和规律，3）研究C-H共价键对电子态和声子振动的影响，4）研究电荷转移机制下的电-声耦合机制。以期：1）通过C做骨架构筑CHx子晶格增强H原子结构在低压下的稳定性，并在化学预压缩的基础上引入电荷转移机制加速体系的金属化相变；2）探索碳骨架下驱动强电-声相互作用的H原子新结构；3）为发展低压（<100 GPa或常压）高温超导体提供新的理论依据。

Recently, the discovery of near-room-temperature superconductivity in hydrides has pushed researchers' interest in the study of hydrides superconductors to a new climax. However, the influence of H atomic structure on the superconductivity in hydride has not been determined, and the pressure of high-temperature superconductivity is still too high (over 100 GPa) to easily realize, so it is necessary to further explore the superconducting mechanism of hydrides and develop low-pressure and high-temperature superconductors. Based on the first-principles calculations, this project focuses on M-CHx (M = alkali, alkaline-earth and rare-earth metal) ternary hydrides with both polar covalent bonds and ionic bonds, 1) studying the structural characteristics and change law of CHx under pressure and metal doping, 2) studying the mechanism of reducing the metallization pressure of the system, 3) studying the effect of C-H covalent bond on the electronic states and phonon vibrations, 4) studying the electron-phonon coupling mechanism under the charge transfer. It is expected that: 1) CHx sublattice is constructed with C as the framework to enhance the stability of H atomic structure at low pressure, and the charge transfer behavior is introduced to accelerate the metallization of the system on the basis of chemical precompression, 2) a navel H atomic structure driving strong electron-phonon interaction under carbon framework is explored, 3) a new theoretical basis is provided for the development of low pressure (< 100 GPa or ambient pressure) high-temperature superconductors.