高压下三元钇钍氢化物的理论研究

Theoretical study of yttrium thorium hydrides under high pressures

寻找新型高温超导材料一直是材料学、凝聚态物理学领域的重要课题.本文采用基于密度泛函理论的第一性原理计算方法,对P6 m^(2)-YThH_(18)的晶体结构、电子性质、晶格动力学稳定性和超导电性进行了研究.结果发现:P6m^(2)-YThH_(18)稳定存在的压强区间是190~300 GPa;P6m^(2)-YThH_(18)的晶体结构是由ThH_(29)笼子和YH_(29)笼子共同组成;在P6m^(2)-YThH_(18)笼型氢化物中氢元素仅含有H原子形式,最短H—H键长为0.1186 nm;与结构中其他元素之间化学键的强度相比,H—H之间的化学键较强;费米能级附近的电子态密度贡献主要来自于H的s轨道电子;当压强P=190 GPa时,P6m^(2)-YThH_(18)笼型氢化物的超导转变温度T_(c)是100.423 K,是潜在的高温超导体;随着压强的增加,P6m^(2)-YThH_(18)相的超导转变温度T_(c)先增加后减小,当压强增加P=250 GPa时,T_(c)值增加至154.630 K.

The search for novel high-temperature superconducting materials has been a significant topic in the fields of materials science and condensed matter physics.In this paper,the crystal structure,electronic,lattice dynamics stability and superconducting properties of P 6 m^(2)-YThH_(18)were investigated using first-principles calculations based on density functional theory.It is found that P 6 m^(2)-YThH_(18)can keep stable in the pressure range from 190 to 300 GPa.The crystal structure of P 6 m^(2)-YThH_(18)is composed of cages formed by ThH_(29)and YH_(29).In P 6 m^(2)-YThH_(18)structure,only monoatomic H is found,where the shortest H-H bond length is 0.1186 nm.Compared to the chemical bonds with other elements in the structure,the chemical bonds between H and H atoms are relatively strong.Moreover,electronic states near the Fermi level mainly originate from s orbital electrons of H.At P=190 GPa,the superconducting transition temperature(T_(c))of P 6 m^(2)-YThH_(18)reaches 100.423 K,indicating its potential as a high-temperature superconductor.With the increase of pressure,theT_(c)value of the P 6 m^(2)-YThH_(18)phase initially increases and then decreases.When the pressure increases to P=250 GPa,theT_(c)value increases up to 154.630 K.