Formation and superconducting properties of predicted ternary hydride
ScYH6 under pressures
Abstract
Ternary metal hydrides play an essential role in the search for
conventional high-temperature superconductors because they can be
synthesized under mild condition 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 as the doped element to perform systematical crystal
structure searches on the Sc-Y-H system under pressure. A new ternary
hydride ScYH6 was found according to PSO calculations, and it presents
high symmetric character below 150 GPa with a Pm-3 structure (cP8), then
a P4/mmm phase (tP8) becomes favorable from 150 GPa. Importantly,
cP8-ScYH6 is dynamically stable under pressure as low as 0.01 GPa with a
Tc of 32.110 K for Coulomb pseudopotential μ∗=0.13, indicating ternary
hydrides are promising candidates in the search for superconductors
which can be synthesized under mild conditions in hydrogen-rich
materials. The analysis through “triangle straight-line method” (TSLM)
compared with enthalpy difference calculations showed the most
reasonable synthesis pathway of ScYH6 is in the whole studied pressure
range. The Tc of ScYH6 takes a linear relationship with pressure up to
52.907 K under 200 GPa. The lattice dynamical calculations demonstrate
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 new element on
superconducting behavior of binary hydrides.