Synthesis, crystal and electronic structure, and optical properties of two new chalcogenide-iodides: Ba3Q4I2 (Q = S, Se)

Abstract

Two new ternary chalcogenide-iodides, Ba₃S₄I₂ and Ba₃Se₄I₂, were synthesized through high-temperature solid-state reactions, and their structures were determined via single-crystal X-ray diffraction. Both compounds are isostructural and crystallize in the monoclinic space group C2/c (no. 15) with unit cell parameters of a = 14.507(4)/15.080(7) Å, b = 10.104(3)/10.400(5) Å, c = 8.206(2)/8.383(4) Å, β = 101.847(4)/103.206(8)°, and Z = 4 for Ba₃S₄I₂/Ba₃Se₄I₂, respectively. The crystal structure of Ba₃Q₄I₂ (Q = S, Se) is constructed from Q₂²⁻ dumbbells and isolated I¹⁻ anions, which are surrounded by Ba²⁺ cations. According to UV/Vis spectroscopy, Ba₃S₄I₂ is a semiconductor with a bandgap of 2.45(5) eV. Quantum-chemical calculations predict that Ba₃S₄I₂ and Ba₃Se₄I₂ are wide bandgap semiconductors with bandgaps of 2.50 and 2.06 eV, respectively. Electron localization function analysis of chemical bonding indicates covalent interactions in the Q₂²⁻ dumbbells.