Syntheses, crystal structures, and electronic properties of Ba8Si2US14 and Ba8SiFeUS14

• Black single crystals of Ba8Si2US14 and Ba8SiFeUS14 have been synthesized at 1223 K.
• Ba8Si2US14 and Ba8SiFeUS14 are semiconductors with band gaps of 1.2 eV and 1.8 eV.
• Ba8Si2US14 and Ba8SiFeUS14 crystallize in a new structure type in the monoclinic system.
• The salt-like structure comprises US6 octahedra and MS4 tetrahedra separated by Ba cations.

Black single crystals of the new compounds Ba8Si2US14 and Ba8SiFeUS14 have been obtained by high-temperature solid-state methods at 1223 K. These isostructural compounds crystallize in a new structure type in space group C2h3 – C2/m of the monoclinic system. The salt-like structure comprises isolated US6 octahedra and MS4 tetrahedra separated by Ba cations. The US6 octahedra form pseudo-layers that are separated by two other pseudo-layers formed by isolated MS4 tetrahedra. These compounds do not show any short S–S interactions. Ba8Si2US14 charge balances with 8 Ba2+, 2 Si4+, 1 U4+, and 14 S2−; Ba8SiFeUS14 can be charge balanced with 8 Ba2+, 1 Si4+, 1 Fe3+, 1 U5+, and 14 S2−. DFT calculations using the HSE functional indicate that the compounds are semiconductors. The calculated band gaps are 1.2 eV and 1.8 eV for Ba8Si2US14 and Ba8SiFeUS14, respectively.

Crystal structure of Ba8M2US14 viewed down the b–axis.Figure optionsDownload as PowerPoint slide