ChemInform Abstract: Three New Chalcohalides, Ba₄Ge₂PbS₈Br₂, Ba₄Ge₂PbSe₈Br₂ and Ba₄Ge₂SnS₈Br₂: Syntheses, Crystal Structures, Band Gaps, and Electronic Structures.

Abstract

Three New Chalcohalides, Ba 4Ge2PbS8Br2, Ba4Ge2PbSe8Br2 and Ba4Ge2SnS8Br2: Syntheses, Crystal Structures, Band Gaps, and Electronic Structures. -Single crystals of the new title compounds are prepared from mixtures of BaQ (Q: S, Se), MQ (M: Sn, Pb), GeQ 2, and NaBr (Ar, silica tubes, 1123 K, 50 h). The compounds are characterized by powder and single crystal XRD, diffuse reflectance spectroscopy, and DFT electronic structure calculations. They crystallize isostructurally in the orthorhombic space group Pnma with Z = 2. The structures contain distorted MQ 5Br octahedra forming chains, which are further connected by GeQ4 tetrahedra to generate a three-dimensional framework with Ba 2+ cations in the channels. Ba4Ge2PbS8Br2, Ba 4Ge2PbSe8Br2 and Ba4Ge2SnS8Br2 have indirect band gaps of 2.054, 1.952, and 2.066 eV, respectively. -(LIN, Z.; FENG, K.; TU, H.; KANG, L.; LIN, Z.; YAO*, J.; WU, Y.; J. Alloys Compd. 611 (2014) 422-426, http://dx.