Syntheses and characterizations of compounds Ba4F4XGa2S6 (X = Cr, Mn, Fe) and Ba4F4MnIn2S6 with 2D layered structures

Four new 2D layered quinary sulfides, Ba4F4CrGa2S6 (1), Ba4F4MnGa2S6 (2), Ba4F4FeGa2S6 (3) and Ba4F4MnIn2S6 (4), have been synthesized by the traditional solid state reaction method. Single crystal X-ray diffraction analyses show that the isostructural complexes 1, 3 and 4 belong to the Ba2F2Fe1.5S3 structure type and crystallize in the space group Pnma of the orthorhombic system, whereas the complex 2 crystallizes in the space group Cmca. The crystal structures of the four compounds can be viewed as the alternated stacking of the fluorite type [Ba2F2](2+) blocks and the newly discovered [X0.5GaS3](2-) or [X0.5InS3](2-) blocks. First-principles electronic structure calculations performed with DFT indicate that the title compounds are semiconductors with the band gaps of 1.83, 3.21, 1.16 and 2.93 eV for 1, 2, 3 and 4, respectively.