Crystal growth and X-ray structure determination of Rb3Bi2I9

The compound Rb3Bi2I9 was synthesized by melting a stoichiometric mixture of RbI and BiI3 and annealing for 1 month some degrees below the melting temperature of 785±5K; a large single crystal of the title compound has been grown from the melt by directional solidification using the vertical Bridgman-Stockbarger technique. X-ray structure determination of the compound involved single-crystal diffractometry, direct and Patterson methods and least-squares refinement. Rb3Bi2I9 exhibits a new type of crystal structure, crystallizing in the monoclinic space group Pc with unit-cell parameters a=14.690(4), b=8.195(2), c=25.645(6) A, β=125.39(2)°, V=2517(2) A3, Z=4. The unit-cell of Rb3Bi2I9 has six pseudohexagonal RbI3 layers which are stacked along the direction near to the normal of the XY plane. Each BiI6 octahedron shares three corners with three other octahedra to form parallel Bi2I9 corrugated layers intersecting Z axis of the structure at an angle near 120°.