高压下Y-Si-H体系晶体结构和超导性质的第一性原理研究

Ab Initio Calculation Principles Study of Crystal Structure and Superconducting Properties of Y-Si-H System under High Pressure

采用第一性原理计算方法,研究了三元氢化物Y-Si-H体系在高压下的晶体结构、电子性质及超导性质,发现了热力学稳定的YSiH_(7)、YSiH_(9)、YSi_(2)H_(12)和YSiH_(18),以及热力学亚稳的YSi_(2)H_(13)、YSi_(2)H_(14)和Y_(2)SiH_(17)。电子性质计算表明,YSiH7为绝缘体,YSi_(2)H_(13)为半导体,其余氢化物均具有金属特性。通过麦克米兰方程估算超导转变温度(T_(c))发现,YSi_(2)H_(12)具有最高的T_(c),在100 GPa下为43.5 K。YSi_(2)H_(14)的动力学稳定压力可降至40 GPa,T_(c)为23.8 K,是Y-Si二元化合物中最高T_(c)的2倍,说明在Y-Si体系中引入H原子可以有效地提高超导转变温度。Y_(2)SiH_(17)在100 GPa下的T_(c)为35.8 K。谱函数和电声耦合计算结果表明,在YSi_(2)H_(14)和Y_(2)SiH_(17)中除中频振动的H原子诱导超导外,低频振动的Y原子也起着重要作用。

Using first principles density functional theory calculations,the crystal structure,electronic properties,and superconductivity characteristics of the ternary hydride Y-Si-H system under high pressure were investigated.The study revealed the existence of thermodynamically stable phases,including YSiH_7,YSiH_9,YSi_2H_(12),and YSiH_(18),and thermodynamically metastable phases,namely YSi_2H_(13),YSi_2H_(14),and Y_2SiH_(17).Electronic properties calculations showed that YSiH_(7) is insulator and YSi_2H_(13) is semiconductor,while the remaining hydrides exhibit metallic properties.Superconducting transition temperatures(T_c) were estimated using the McMillan equation,with YSi_2H_(12) hosting the highest T_(c) of 43.5 K at 100 GPa.The dynamic stable pressure of YSi_2H_(14) can be reduced to 40 GPa,and its Tc is 23.8 K which is twice the highest T_(c) among binary Y-Si compounds,indicating that introducing H atom into Y-Si system can effectively increase the superconducting transition temperature.Y_2SiH_(17) exhibits a T_(c) of 35.8 K at 100 GPa.Spectral function and electron-phonon coupling calculations suggested that in YSi2H14 and Y_2SiH_(17),in addition to the H-induced superconductivity from mid-frequency vibrations,low-frequency vibrations of Y also play a significant role for superconductivity.