Neutron diffraction studies of polyiodides. I. Potassium triiodide monohydrate

The crystal structure of KI a. H20 has been determined directly from neutron diffraction data giving Rr2 = 0.027. This compound crystallizes in the monoclinic space group Pc with a = 4.629 (1), b = 10.047 (3), c = 9.662 (3) A, fl = 116.51 (1) °, Z = 2. The linear 13 ions are arranged in planes in a mutually perpendicular manner and are found to be very nearly symmetric [I-I = 2.925 (3), 2.935 (3)A]. The K ÷ ion and the water molecule are between the iodine planes, each water molecule being coordinated to two K + ions.