Pressure-induced stable structures and physical properties in Sr-Ge System

Abstract In this work, we have systematically performed structure searching for Sr-Ge system under pressure up to 200 GPa and found six stable stoichiometries as Sr 3 Ge, Sr 2 Ge, SrGe, SrGe 2 , SrGe 3 and SrGe 4 . We demonstrated the interesting structure evolution behaviors in Sr-Ge system with increased germanium content, the Ge atoms arranging from isolated anions in Sr 3 Ge, chains in Sr 2 Ge, square units in SrGe, trigonal units and hexahedrons in SrGe 2 , cages in SrGe 3 , hexagons and Ge 8 rings in SrGe 4 . The structural diversity produces various manifestations of electronic structures, which are benefit for electrical transportation. Among them, these novel phases with metallic structures show superconductivity (maximum T c ~ 8.94 K for Pmmn Sr 3 Ge). Notably, the n -type semiconducting Pnma SrGe 2 structure exhibits high Seebeck coefficient and excellent electrical conductivity along y direction, leading to a high ZT value up to 1.55 at 500 K, which can be potential candidates as high-performance thermoelectrics. Our results would enable the development of fundamental science in condensed matter physics and potential applications in novel electronics or thermoelectric materials.