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

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 YSiH₇, YSiH₉, YSi₂H₁₂, and YSiH₁₈, and thermodynamically metastable phases, namely YSi₂H₁₃, YSi₂H₁₄, and Y₂SiH₁₇. Electronic properties calculations showed that YSiH₇ is insulator and YSi₂H₁₃ is semiconductor, while the remaining hydrides exhibit metallic properties. Superconducting transition temperatures (T_c) were estimated using the McMillan equation, with YSi₂H₁₂ hosting the highest T_c of 43.5 K at 100 GPa. The dynamic stable pressure of YSi₂H₁₄ can be reduced to 40 GPa, and its T_c 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. Y₂SiH₁₇ exhibits a T_c of 35.8 K at 100 GPa. Spectral function and electron-phonon coupling calculations suggested that in YSi₂H₁₄ and Y₂SiH₁₇, in addition to the H-induced superconductivity from mid-frequency vibrations, low-frequency vibrations of Y also play a significant role for superconductivity.