Ba3GeS5 and Ba3InS4Cl: Interesting size effects originated from the tetrahedral anions

• Two new barium chalcogenides, Ba3GeS5 and Ba3InS4Cl, were synthesized from the BaCl2-flux reactions.
• Their crystal structures feature discrete [MS4] tetrahedra which embody interesting size effects.
• Both compounds exhibit a band gap around 3.0 eV.
• They are thermally stable up to 1073 K.

Two new barium chalcogenides, Ba3GeS5 and Ba3InS4Cl, were synthesized by using high temperature solid-state reactions and their structures were determined by single-crystal X-ray diffraction technique. Despite the similar chemical formula, the structures of Ba3GeS5 and Ba3InS4Cl are subtly different due to the size effects originated from the tetrahedral anions. Ba3GeS5 crystallizes in the orthorhombic space group Pnma (no. 62) with cell parameters of a=12.0528(9) Å, b=9.5497(7)  Å and c=8.5979(6)  Å, while Ba3InS4Cl adopts a different tetragonal system (space group: I4/mcm, no. 140, a=b=8.3613(6) Å, c=14.3806(18) Å). The measured optical band gap of Ba3GeS5 is 3.0 eV, a little smaller than the value of 3.42 eV in Ba3InS4Cl. Theoretical calculations by Wien2k are provided as well in order to better understand these results.

The polyhedral structure view for Ba3GeS5 and Ba3InS4Cl in which Ba, S and Cl atoms are plotted in purple, red and green spheres.Figure optionsDownload as PowerPoint slide