X-ray study of CsCdI3 · H2O

Abstract

Abstract Structure determination at 295 K on a single crystal of cesium triiodocadmiate hydrate, CsCdI3 · H2O, was performed on a CAD-4 diffractometer with MoKα radiation. The crystal structure is monoclinic, space group Pc, with a = 9.000(1) Å, b = 7.565(1) Å, c = 14.970(3) Å, β = 90.47(1)°, V = 1019.3(2) Å3, Z = 4, D x = 4.197(1) g cm−3, μ = 145.5 cm−1, F(000) = 1088. A final least-squares refinement resulted in an R value of 0.041 for 1736 unique observed reflections with I > 3σ(I). The positions of H atoms were not determined. CsCdI3 · H2O is built up from one-dimensional chains of corner-sharing CdI4 tetrahedra running along [100]. The bridging Cd–I distances are in the range 2.84 Å–2.86 Å, while non-bridging Cd–I bonds are 2.73 Å–2.74 Å. The Cs atoms are ten coordinate with two water molecules at 3.04 Å–3.14 Å and eight I atoms at 3.83 Å–4.55 Å. The Cs coordination is described as a deformation of a centaur polyhedron based on the cube and the icosahedron. There are pseudo-mirror planes parallel to (100) and pseudo 21 axes parallel to [001], corresponding to the orthorhombic space group Pmc21. The Cd atoms and two thirds of the I atoms are in the pseudo-mirror planes. However, the pseudo symmetry relates Cs atoms with water molecules.