The crystal structure of Cu4Bi4Se9

The crystal structure of Cu4Bi4Se9, synthesized at 400 °C, was determined from single crystal X-ray diffraction data and refined to the R1value of 0.05. The compound is orthorhombic, with a= 32.692 Å, b= 4.120 Å, and c= 12.202 Å, space group Pnma. The structure contains three square pyramidal Bi sites, an octahedrally coordinated Bi site as well as two tetrahedrally and two irregularly coordinated Cu sites. The structure is an intergrowth of PbS-like slabs with irregularly configured slabs of Bi pyramids and Cu tetrahedra. It contains covalently bonded Se2groups. Isotypy with Cu4Bi4S9is connected with substantial changes in coordination details for two out of five distinct Cu sites. Modular relationships to the structures of the cuprobismutite series of Cu—Bi sulfosalts can be expressed as different ways of recombination of the same large structural fragment in the structures of Cu4Bi4Se9and of the first cuprobismutite homologue, Cu4Bi5S10.