Syntheses, crystal and electronic structures, and characterizations of the mixed anions compounds Ba4In2Te2Q5 (Q = S, Se)

Abstract

Two new quaternary chalcogenides, Ba₄In₂Te₂Q₅ (Q = S, Se), have been synthesized by using a conventional high-temperature solid-state reaction method. These two isostructural compounds crystallize in the space group P4/mbm (127), with a = b = 8.3669(9) Å, c = 11.0397(15) Å, and Z = 2 for Ba₄In₂Te₂S₅ (1) and a = b = 8.6021(4) Å, c = 11.3047(9) Å, and Z = 2 for Ba₄In₂Te₂Se₅ (2) at room temperature. The special structural feature of the compounds is the unique dimeric [In₂Te₂Q₄]⁶⁻ units by the ordered arrangement leading to the covalent layer. First-principles electronic structure calculation by density functional theory (DFT) shows that the two compounds are both indirect-band semiconductors with band gaps of 2.07 eV for 1 and 1.75 eV for 2, respectively.