Structure and Electronic Properties of Fe₂SH₃ Compound under High Pressure

Inspired by the diverse properties of hydrogen sulfide, iron sulfide, and iron hydrides, we combine first-principles calculations with structure prediction to find stable structures of Fe-S-H ternary compounds with various Fe_xS_yH_z (x = 1-2; y = 1-2; z = 1-6) compositions under high pressure with the aim of finding novel functional materials. It is found that Fe₂SH₃ composition stabilizes into an orthorhombic structure with Cmc2₁ symmetry, whose remarkable feature is that it contains dumbbell-type Fe with an Fe-Fe distance of 2.435 Å at 100 GPa, and S and H atoms directly bond with the Fe atoms exhibiting ionic bonding. The high density of states at the Fermi level, mainly coming from the contribution of Fe-3d, indicates that it satisfies the Stoner ferromagnetic condition. Notably, its ferromagnetic ordering gradually decreases with increasing pressure, and eventually collapses at a pressure of 173 GPa. As a consequence, magnetic and nonmagnetic transition can be achieved by controlling the pressure. In addition, there is a very weak electron-phonon coupling in Cmc2₁-structured Fe₂SH₃. The different superconducting mechanisms between Fe₂SH₃ and H₃S were compared and analyzed.