Syntheses, crystal and electronic structure of a series of quaternary rare-earth sulfides MgRE6Si2S14 (RE = Y, Ce, Pr, Nd and Sm)

Abstract

Five isostructural quaternary rare-earth sulfide MgRE6Si2S14 (RE = Y, Ce, Pr, Nd and Sm) have been successfully synthesized via high-temperature solid-state method. They crystallize in the hexagonal space group P63 and belong to the MnLa6Si2S14 structure type. Their 3-D structures are constructed by the connection between infinite 1-D [(RE6S6)6+]∞ tubular and (SiS4)4– tetrahedron, and Mg2+ ions occupy the octahedral interspaces in the [(RE6S6)6+]∞ tubular. The lanthanide contraction phenomenon among these compounds is also discussed. Electronic structure calculation indicates that MgY6Si2S14 has an indirect optical energy gap of 2.26 eV, and its optical absorption is mainly ascribed to the charge transition from S-3p to Y-4d states.