THE ROOM-TEMPERATURE PHASE OF (CH3NH3)(3)BI2CL9

The structure of (CH3NH3)(3)Bi2Cl9 was determined at room temperature. It is orthorhombic, space group Pnma, with four formula units in the unit cell of dimensions a = 20.43(3), b = 7.71(1) and c = 13.26(2) A. The structure was refined to R = 0.045 for 911 non-equivalent observed reflections. It is formed by infinite Bi2Cl93- polyanions which form zig-zag double-chains running along [010]. The chains are separated by three crystallographically inequivalent CH3NH3+ cations. The structur e consists of a close-packed arrangement of CH3NH3+ cations and Cl- an ions, with the stacking direction parallel to [100]. The Bi3+ occupy e xclusively Cl- coordinated octahedral voids in this packing. The Bi3coordination is distorted by the stereoactive 6s(2) lone pair.