Bismuth triiodide free of stacking faults was obtained by synthesis fr
om the elements and sublimation in quartz tubes. X-ray investigations
using a twinned crystal (space group R $($) over bar$$ 3 (No. 148), a
= 752.49(3) pm, c = 2073.3(1) pm, V = 1016.7(2). 10(6) pm(3)) confirme
d the rhombohedral stacking sequence of BiI3 layers. The bismuth atoms
are shifted about 4 pm along the c axis out of the centres of the oct
ahedral sites. The stacking order of BiI3 layers is discussed.