Crystal structure of calcium perchlorate anhydrate, Ca(ClO 4 ) 2 , from laboratory powder X-ray diffraction data.

The crystal structure of calcium perchlorate anhydrate was determined from laboratory X-ray powder diffraction data. The title compound was obtained by heating hydrated calcium perchlorate [Ca(ClO4 )2 · x H2 O] at 623 K in air for 12 h. It crystallizes in the ortho-rhom-bic space group Pbca and is isotypic with Ca(AlD4 )2 . The asymmetric unit contains one Ca, two Cl and eight O sites, all on general sites (Wyckoff position 8 c ). The crystal structure consists of isolated ClO4 - tetra-hedra and Ca2+ cations. The Ca2+ cation is coordinated by eight O atoms of eight symmetry-related ClO4 - tetra-hedra within a distorted square-anti-prismatic environment.