Formation and superconducting properties of predicted ternary hydride ScYH6 under pressures

Ternary metal hydrides play an essential role in the search for conventional high-temperature superconductors because they can be synthesized under mild conditions and recovered at ambient pressure. It has been widely accepted that the electronic structure, metallization pressure, and superconducting behavior of binary hydrides can be adjusted effectively by doping, replacing, or introducing a new element. In this work, yttrium hydrides were chosen as parent hydrides, while scandium was considered the doping element to perform systematical crystal structure searches on the Sc-Y-H system under pressure. A new ternary hydride ScYH(6)with a Pm-3 structure (cP8) was found below 150 GPa according to Particle Swarm Optimization calculations, and then, a P4/mmm phase (tP8) becomes favorable from 150 GPa. Importantly, cP8-ScYH(6)is dynamically stable under pressure as low as 0.01 GPa with a superconducting temperature (T-c) of 32.110 K for Coulomb pseudopotential mu* = 0.13, indicating that ternary hydrides are promising candidates in the search for superconductors that can be synthesized under mild conditions in hydrogen-rich materials. The analysis using the "triangle straight-line method", compared with enthalpy difference calculations, showed that the most reasonable synthesis pathway of ScYH(6)isScH(3) + YH3 -> ScYH(6)in the whole pressure regime studied in this work. TheT(c)of ScYH(6)has a linear relationship with pressure up to 52.907 K under 200 GPa. The lattice dynamical calculations demonstrate that the H atoms in both cP8 and tP8 structures make crucial contributions to the superconducting behavior of ScYH6. These findings can further reveal the influence of doping, replacing, and introducing element on the superconducting behavior of binary hydrides.