A double-layered hydroxide, 3CaO center dot Al2O3 center dot CaI2 center dot 10H(2)O

The title compound, calcium oxide-dialuminium trioxide-calcium iodide hydra te (3/1/1/10), also formulated as Ca2Al(OH)(6)I . 2H(2)O (dicalcium alumini um hydroxide iodide dihydrate), belongs to the AFm family of phases, which are hydrated products commonly encountered in cement paste. It also belongs to the more general category of compounds called lamellar double hydroxide s (HDL). Its structure can be considered very close to that of the equivale nt disordered sulfate compound, with the ordered I- anions replacing the di sordered SO42- groups. It consists of positively charged main layers, [Ca2A l(OH)(6)](+), and negatively charged interlayers, [I-,2H(2)O], where I and O atoms occupy ordered sites. Al3+ and Ca2+ cations are six- and seven-coor dinate, respectively, and all water molecules are bonded to Ca2+ cations to assume the seventh coordination position. I- anions are surrounded by ten H atoms, six from hydroxyl groups and four from water molecules. These anio ns are therefore connected to the main layers by ten I-H hydrogen bonds, si x of 3.10(4) Angstrom and four of 2.78 (8) Angstrom, where the donors are h ydroxyl groups and water molecules, respectively.