Syntheses, Structures, and Theoretical Study of LaCuSTe and SmCuSTe.

Area of Science:

• Solid State Chemistry
• Materials Science
• Crystallography

Background:

• Mixed-chalcogen compounds offer tunable electronic properties.
• Lanthanum (La) and Samarium (Sm) based chalcogenides are of interest for their potential applications.
• Understanding structure-property relationships in novel materials is crucial for materials design.

Purpose of the Study:

• To synthesize and characterize new mixed-chalcogen compounds LaCuSTe and SmCuSTe.
• To determine the crystal structures of these novel compounds.
• To investigate their electronic properties and the effect of composition on the band gap.

Main Methods:

• Synthesis of LaCuSTe and SmCuSTe via high-temperature reactions of constituent elements at 1123 K.
• Single-crystal X-ray diffraction for precise crystal structure determination.
• Band structure calculations to predict semiconductor behavior and electronic properties.

Main Results:

• LaCuSTe crystallizes in the monoclinic system (P2(1)/c) with a structure related to LaCuS2.
• SmCuSTe adopts a new structure type in the orthorhombic system (Pbca).
• Both compounds exhibit layered structures with (CuSTe)(n) sheets separated by rare-earth atoms, featuring unique coordination environments for La/Sm and Cu atoms. Band structure calculations confirm semiconducting behavior, with Te substitution reducing the energy gap.

Conclusions:

• The successful synthesis and structural elucidation of LaCuSTe and SmCuSTe expand the family of mixed-chalcogen rare-earth compounds.
• The distinct layered structures and coordination polyhedra highlight novel structural motifs in these materials.
• The compounds are predicted to be semiconductors, with potential for tuning their electronic properties through chalcogen substitution.