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Synthesis, Crystal, and Electronic Structure of Ba 3 Sb 2 Q 7 ( Q = S, Se)

2015; Wiley; Volume: 641; Issue: 6 Linguagem: Inglês

10.1002/zaac.201500126

1521-3749

Jian Wang, Kathleen Lee, Kirill Kovnir,

Inorganic Chemistry and Materials

Abstract Two new barium antimony chalcogenides, Ba 3 Sb 2 S 7 and Ba 3 Sb 2 Se 7 , were synthesized from elements by high‐temperature solid‐state reactions. The crystal structures were determined by means of single‐crystal X‐ray diffraction. Both compounds are isostructural and crystallize in a new structure type in the monoclinic space group C 2/ c (No. = 15) with unit cell parameters of a = 18.305(2)/18.904(5) Å, b = 12.202(1)/12.651(3) Å, c = 13.117(1)/13.554(3) Å, and β = 110.134(1)/109.839(4)° for Ba 3 Sb 2 S 7 /Ba 3 Sb 2 Se 7 , respectively. The crystal structures are comprised of Ba cations, trigonal‐pyramidal [Sb Q 3 ] 3– , and [Sb Q 4 ] 3– units ( Q = S, Se). In the Sb Q 4 unit, one vertex is a Q 2 dumbbell instead of a single Q atom. Quantum‐chemical calculations show that the sulfur‐containing compound is an indirect semiconductor with a high density of states below the Fermi level. ELF analysis shows highly polarized Sb–S bonds and unusual torus‐shaped ELF distributions around the terminal sulfur atom of the S 2 dumbbell. According to UV/Vis measurements Ba 3 Sb 2 S 7 is an indirect semiconductor with a bandgap of 2.1 eV.