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

Abstract

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.